Month: November 2024

The 2025 TumbleStone Calendar features beach stones collected during my two South Island fossicking trips in 2024. Details about the stones shown in the previous months can be found here: January and February (Gemstone Beach and Slope Point), March and April (Kakanui and Gemstone Beach), May and June (Ward Beach and Kakanui), July and August (Slope Point and Gemstone Beach), and September and October (Gemstone Beach and Ward Beach). November’s stones come from Seadown Beach, Kakanui, and December features more stones from Gemstone Beach. All of the stones in the Calendar were photographed in the rough while wet, held in my hand in bright sunlight.

NOVEMBER – SEADOWN BEACH, KAKANUI

The beaches on the North Otago coast between Oamaru and the mouth of the Waianakarua River are often stony, though the amount of stones and the degree of their smoothness vary considerably. On page 116 in her book, “The New Zealand Rockhound” (1981), Natalie Fernandez lists three places here as good for hunting interesting stones: All Day Bay, Kakanui River, and Waianakarua River. Seadown Beach lies a few kilometres north of these locations. It was in June 2020 that I first explored this coastline and stumbled across this beach, two kilometres north of the village of Kakanui. I found a number of gorgeous quartzites and jaspers there, and it quickly became one of my favourite fossicking sites. I named it Seadown Beach as Seadown Road intersects the main coast road here. November’s beach scene of Seadown Beach (below, left) was photographed on 30 September 2024, on my way home from my final fossicking trip this year.

I had two fossicks that day and the beach photo was taken at 3.30pm when it was approaching high tide. Stones 3 and 4 for the month were found that same day, but in the morning. I found Stone 1 the next day, on 1 October. It is what is known as a plasma jasper stone.

Plasma jasper has dark green within it – see The Quartz Page. Encyclopaedia Britanica notes: “Its colour, various shades of green, is due to disseminated silicate particles of different kinds – e.g., amphibole or chlorite.” I was not aware of this kind of stone before and initially thought it might have been limonite prase which can be found along the North Otago coast. However, a member of the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils” suggested the ID of plasma jasper to me recently.

Stone 2 is a beach agate, a chalcedony stone, a cryptocrystalline form of silica (see Wikipedia on chalcedony). I picked it up on Seadown Beach on 5 September. Here it is, held up to the sunlight.

Beach agates are often found on the North Otago and Canterbury coast. Chalcedony is usually translucent, allowing some light to pass through it. However, the presence of minerals within it can block the light and give rise to interesting shapes. The following is Stone 2 without the light behind it:

Sometimes the term “agate” is reserved for chalcedony with bands inside it. The presence of significant amounts of opaque minerals within chalcedony results in stones like jasper – see Rocktumbler.com.

Stone 3 is a specimen of a type of stone I first found on Seadown Beach in June 2022. I picked it up on 30 September, and it contains lots of tiny bryozoan fossils.

Bryozoans are one-celled animals which live in colonies. There are about 1,500 living species. Most marine bryozoans have a partially calcified, hard body wall, which is subject to the process of fossilisation. There are many different types of bryozoa, some shaped like branching twigs, some like fans, some lacy. A 2022 news article notes they are often known as “moss animals”, because the bushy-looking live ones look like moss, the literal meaning of bryozoa from the Greek, bryon meaning moss, zoön meaning animal. More details are available in this Post on the Seadown stones.

Stone 4 is an “unknown” stone. It kind of looks like a mudstone but has light-coloured orb-like features in it that I have not seen in mudstone before.

Sometimes, I know, such orbs result from the clustering of light-coloured minerals during rock formation. I have found maybe three of these stones on Seadown Beach, this one being picked up on 30 September.

DECEMBER – GEMSTONE BEACH

The busiest part of Gemstone Beach is always the 100 to 200 metres in front of the carpark. December’s beach scene captures that area just after noon on a Friday on 23 February. There are 21 people and two dogs present.

December’s Stone 1 is a jasper, a variety of opaque microcrystalline quartz. It was found, along with Stones 2 and 3, during a three hour fossick on a cold morning, on 8 September. The light-coloured flashes caught my eye on the beach.

I started tumble-polishing this stone yesterday.

Stone 2 is a grey banded argillite. Sediments of light and dark mud have been captured in the stone.

This is quite a large stone at nine centimetres in length. It is too big to tumble-polish so I have given it a home in the rock garden beside our garage which has an attached AirBnB apartment called “The Stones”. It has rained today so I took some photos of it.

Even when dry, the distinctive bands of Stone 2 can easily be seen. Brown banded argillite (see here) and green banded argillite (see Stones Gn8 to Gn13 in this Post) can also be found on Gemstone Beach. For examples of banded argillite from Montana, USA, see West Valley Naturalists – this shows that the banding on many of the Gemstone Beach stones is by comparison clear and well-defined.

Stone 3 is another jasper but its character is different from that of Stone 1.

The green in it is likely due to epidote. Jasper comes in a wide range of varieties.

Stone 4 caught my eye on the beach because of the darker mineral that lies in-between the lighter coloured fragments. Maybe this is a breccia.

The close-ups reveal the many tiny crystals that make up the stone, maybe of quartz. My guess is that the greenish-grey bands between the light coloured fragments could be epidote. However, this is a very unusual stone in my experience and I am unsure what it is.

This 2025 Calendar is for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.

The 2025 TumbleStone Calendar features beach stones collected during my two South Island fossicking trips in 2024. Details about the stones shown in the months of January and February are here, in March and April here, in May and June here, and in July and August here.

The first month in this Post, the month of September, is another featuring Southland’s Gemstone Beach (Southland). October takes us back to Ward Beach (Marlborough), first encountered in the month of May. The stones in this Calendar were photographed in the rough while wet, held in my hand in bright sunlight. Often the photos reveal much more about the stones than I initially noticed when I picked them up. Also note that my identifications of stone types are generally tentative.

SEPTEMBER – GEMSTONE BEACH

This is what a British newspaper, “The Guardian”, wrote in September 2024, in a long and interesting article about Gemstone Beach and its people: “At a distance, the stones look like any others found along New Zealand’s rugged Southland coast, but here, at Orepuki – or Gemstone Beach – a closer look reveals a bed of riches. Jasper, hydro-grossular garnet in pinks, greens and yellows, patterned fossilised worm-trails, spotted argillite, frosty white quartz, speckled granites, pink-flecked rhodonite and – in rare cases – the unmistakable blue of sapphire, colour the low-tide line.” Such articles tend to emphasise the “precious gemstones” to be found on Gemstone Beach but in reality the stones effectively have no monetary value. Maybe some of the colourful ones and some of the hydrogrossular garnets can be polished and made into low-cost jewelry, and maybe a collector might pay a little for one of the beach’s rare low-quality sapphires. But the real “treasures” to be found on Gemstone Beach are the gorgeous colourful “ordinary” stones that are remarkable for their natural beauty. You can find stones like these on many New Zealand beaches, but they seem to be more numerous and more concentrated at Gemstone Beach and the nearby coast of Te Waewae Bay. The month of September in the 2025 TumbleStone Calendar features four of Gemstone Beach’s treasures collected by me in 2024. The beach scene was captured on 21 March during my final fossick there for my first trip for 2024, though it does not feature in the Blog Post for that day.

September’s Stone 1 is a small hydrogrossular garnet, found on 27 February, though it is an unusual black and white colour for a garnet.

Gemstone Beach is particularly well known for its hydrogrossular garnets. These stones usually feel waxy and they shine brightly when wet, outshining even quartz. Hydrogrossular garnet is one of 13 minerals first described from New Zealand and accepted as valid by the International Mineralogical Association. There is an introduction to hydrogrossular garnets, along with nine specimens, in “First Identified in New Zealand in 1943 – Revisiting the Hydrogrossular Garnets of Gemstone Beach”. A lot more detail and many more specimens can be found on the TumbleStone Two page about Hydrogrossular Garnet.

Gemstone Beach’s Stone 2 for September is an unknown one to me. It was the areas of colour against a dark background that caught my eye on the beach on 25 September.

Its texture kind of reminds me of schist, because of its relatively coarse grain, with some added colour from a pinkish mineral. But I don’t know enough about schist for sure or to say much more. See University of Auckland Geology for a description of schist as a metamorphic rock.

Stone 3 for the month of September is another epidote. April’s Stone 2 was a type of orbicular epidote, I suggested. September’s Stone 3 has a more intense shade of green to it, brought out by the small patches of white and light grey.

Stone 4 is the third of three poppy jaspers to appear in the Calendar, the other two being January’s Stone 3, with larger orbs, and July’s Stone 4, with smaller orbs. Again hematite is present in the stone, adding to the intensity of the red.

All of the poppy jaspers I have found on Gemstone Beach have been small and have often been chipped. None have been bigger than three centimetres long, usually being even smaller. Not many of them can be tumble polished successfully due to their rough condition.

OCTOBER – WARD BEACH

Ward Beach in Marlborough features in three “Geotrips”. GeoTrips are guides to rock outcrops, geological displays or landforms that can be visited and explored in New Zealand. They have been compiled by GNS Science with the assistance of geologists and knowledgeable enthusiasts. Useful background information is provided, along with photos, maps, and directions how to get there. The first Geotrip to Ward Beach is entitled “Uplift at Ward Beach”. During the 14 November 2016 Kaikōura Earthquake, this part of the coastline was uplifted around 2.2 to 2.6 metres. “The change in ground level at Ward Beach has forced the Flaxbourne River to abandon its estuary and incise through the former estuary bed and gravel beach deposits, exposing more of the bedrock beneath.” The first two photos below show the uplift.

The second Geotrip takes readers to the Ward Beach boulders, 800 metres from the carpark (best visited at low tide). The third and fourth photo above illustrate this Geotrip. “These brown spherical rocks are concretions within Late Cretaceous (more than 65 million years ago) marine sediments… They consist of dolomite (calcium magnesium carbonate) that formed over several million years within a mudstone… Concretions usually start around a piece of wood, fossil or a shell and grow radially outwards by the precipitation of mineral cement.” Chancet Rock Reserve, the subject of the third Ward Beach Geotrip, is important because there, 1,500 metres north of the carpark, is an accessible outcrop where you can see the K-Pg boundary layer (formerly known as the K-T boundary) – see the fifth and sixth photos above. “The Cretaceous-Paleogene boundary was identified and confirmed by the presence of the ‘iridium anomaly’ with tens of times the normal concentration of iridium (a very rare metal) in a thin clay layer. This layer has been recognised worldwide and marks the end of the Age of the Dinosaurs, caused by a devastating asteroid impact that struck part of where Mexico’s Yucatan Peninsula is today.”

The month of October in the TumbleStone 2025 Calendar features four Ward Beach stones. I found all four stones on the same day, on 2 October, during a two hour fossick. The next day I caught the Cook Strait ferry on my way home.

Stone 1 is limestone with dark trace fossils through it.

On page 31 of “Gemstones”, Jocelyn Thornton has two specimens of “grey limestone with bands of worm trails like rows of arrowheads”. These can be found along the Marlborough coast and are common on Ward Beach. But there is a great diversity of these, with different trace fossil shapes, as can be seen in this Post. On the beach, when dry, these stones are dull and a cloudy white (see photos below). You have to look close to see anything in them and even then the details are not disclosed. You need to see them wet to discern their traces better.

Limestone is relatively soft and won’t stand up to the usual tumble-polishing process. Simply tumbling them for a couple of days in fine grit keeps them looking clear, even when dry.

October’s Stone 2 is a small jasper found on Ward Beach.

It is brecciated and has a large quartz vein at the top. Jocelyn Thornton has a number of examples of New Zealand jasper on pages 17 and 18 of “Gemstones”.

Stone 3 is, I think, what is called a magpie agate. Its black and white colour is what is shared with the magpie bird.

The black is likely to be flint and the white will be chalcedony, also known as agate. Chalcedony is a cryptocrystalline form of silica, which means that its crystals are less than 0.001 mm in size, too tiny to see even using a hand lens.

Stone 4 is a brecciated yellow jasper. Sometimes such a stone is called a storm jasper. It appears to have some quartz in it as well.

Miami Mining notes that the yellow colour is due to iron oxide: “Yellow jasper is known for its bright and bold colors, which are caused by the presence of iron oxide (hematite) within the gemstone. The amount and distribution of hematite within the gemstone can vary, resulting in a range of colors from pale yellow to deep orange and red.” Craftstones argues along similar lines, with an addition: “The presence of iron oxide (the mineral responsible for its colouring) pigments the compound [jasper], resulting in its distinctive colouring and patterns across the surface of the stone. This is very similar to the process in which red jasper is pigmented, however the iron [oxide] is exposed to significantly higher temperatures to achieve a rich yellow.”

The months of November (Seadown Beach, Kakanui) and December (Gemstone Beach) in the 2025 TumbleStone Calendar are featured in the next Post. These 2025 Calendars are for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.

The 2025 TumbleStone Calendar features beach stones collected during my two South Island fossicking trips in 2024. Details about the stones shown in the months of January and February are here, in March and April here, and in May and June here. The month of July is another featuring Southland’s Gemstone Beach and August takes us back to Slope Point, first encountered in the month of February. The stones in this Calendar were photographed in the rough while wet, held in my hand in bright sunlight. Often the photos reveal more about the stones than I noticed when I picked them up on the beach. Also note that my identifications of stone types are generally tentative, and should not be relied on unless previous Blog Posts provide good evidence for them.

JULY – GEMSTONE BEACH

Gemstone Beach is right next to the small town of Orepuki in Southland. It lies 70 kilometres west of Invercargill. The mountains of eastern Fiordland can be seen from it, further to the west. The beach is on the Te Waewae Bay coast, on the shores of Foveaux Strait. The name “Gemstone Beach” most narrowly applies to a 200 to 250 metre stretch of beach in front of the carpark opposite the “Gemstone Beach” road sign. However, I use the name to refer also to the beach that runs from the carpark to the mouth of the Waimeamea River, 1.5 kilometres to the northwest. July’s beach photo, featuring a female Paradise Shelduck, was taken not far from the Waimeamea River on 8 September during a three hour morning fossick that was my first on Gemstone Beach for that trip.

July’s Stone 1 is a trace fossil in argillite. One large trace fossil dominates the stone,seen from the side, but there are a number of other light-coloured “patches” in the stone, some of which are likely to be trace fossils viewed from the top (or bottom).

The local name for this trace fossil is a fossil “worm cast” as it looks a bit like what a worm throws up on the surface after soil has passed through the worm’s body. The trace fossil is what has been left behind after a small animal has burrowed through the sediment at the bottom of the sea or has crawled along its surface about 250 to 300 million years ago. It’s probably not been left by an earthworm. The shape of the trace, a line of chevrons, is known as “protovirgularia”. More information can be found in “I” is for “Ichnogenus Protovirgularia” and “The Tattooed Rock, The Trace Fossils… Revisiting Gemstone Beach’s Trace Fossil Stones”. Argillite is a hardened mudstone, one of New Zealand’s basement rocks. See University of Auckland Geology for a brief account.

I found July’s Stone 2 on Gemstone Beach on 18 February. I have labelled it a quartzite but it might be a brecciated quartz.

What I find most appealing in stones like this is the delicate tracery of mineral colour through it.

I have suggested that Stone 3 could be “Rondonite” but that should read “Rhodonite”, my only spelling mistake in the early versions of this Calendar. Rhodonite is a pink manganese silicate mineral usually associated with black manganese oxides which may occur as dendrites, fracture-fillings, or matrix within the stone (Geology.com). Jocelyn Thornton has three examples of rhodonite on page 26 of “Gemstones”. It is the pink and black combination that we use to identify rhodonite and to distinguish it from the likes of thulite, another pink stone with manganese in it (see Stone 4 in the month of April).

Te Ara The Encyclopedia of New Zealand notes: “Rhodonite, a pink manganese mineral, is found as lens-shaped deposits within schist in Otago and the Southern Alps. It usually occurs naturally with a rind of black, oxidised material called pyrolusite.” The best quality and most well-known rhodonite in New Zealand is found near Akatore Creek, south of Dunedin. The Otago Rock and Mineral Club for many years held the mining rights to this source. I have found a couple of stones on Gemstone Beach that could be rhodonite, July’s Stone 3 being the best specimen, found on 20 March this year. I note that Marion Troon’s tray of stone specimens from Gemstone Beach includes a rhodonite – see about halfway though the September 2024 “The Guardian” article on Gemstone Beach.

Stone 4 is a small poppy jasper (orbicular jasper), with some hematite in it, that I found on 22 September.

Compared to January’s Stone 3, another poppy jasper, the “poppies” or orbs are quite small, consisting of tiny dots. According to Wikipedia, “In highly silicified rhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle-like crystals which provide the basis or seed for the orbicular structure seen in this kind of jasper.” For more information, see “O is for Opaque Orepuki Orbicular Jasper”. A great diversity of orbicular jasper exists across the globe, as can be seen in Mindat (the images below come from there).

The poppy jaspers I have found on Gemstone Beach, and that other people find elsewhere in New Zealand, compare well within such diversity.

AUGUST – SLOPE POINT

We visited Slope Point in this Calendar in February. In her booklet, “Gemstones” (1985), Jocelyn Thornton has an entry on Slope Point. She writes on page 35: “On the Southland coast between Waipapa Point and Haldane there are a few pebbly beaches visited by fishermen and rock collectors. The cliffs contain layers of conglomerates with pebbles which weather out and collect on the beaches. At first glance they appear dark, but closer examination reveals a multitude of subtle colours and patterns.” The photo of the beach below was taken during a visit there on 13 March, which is when this month’s Stone 1 was collected. The beach photo was taken from under the high cliffs to the north of the bay, looking across the pebble beach and solitary holiday home to the walking track that slopes down to it.

Stone 1 is an example of a type of stone that I have found a few times here. On the early print runs of the Calendar, I labelled it as “Rhyolite”. However, further thought led me to change that to “Volcanic Breccia”, though most if not all the fragments in it are likely to be rhyolite.

I initially thought that the small white bits in the stone were likely to be crystals, hence the thought that it was rhyolite. However, there are clearly larger bits (clasts) in the stone as well, some consisting of alternating dark and light bands. These will have come from different pieces of stones. As I noted in relation to February’s Stone 2, also a Slope Point breccia, a “breccia” consists of small pieces of rock (clasts) that have not been rounded much by transport by, for example, water before being cemented together. This contrasts with a “conglomerate” which consists of more rounded clasts indicating some erosion before being cemented together and thus having travelled further before formation. The clasts may be the result of faulting (even small movements in rocks caused by tectonic pressure) or a landslide or a volcanic eruption. Of course, some stones can consist of both sharp-edged and rounded clasts, confusing the categorisation!

20 November: I have just finished tumble-polishing Stone 1. The result is very good, with a significant clarification of the stone’s features and a permanent shine.

There are large conglomerate boulders on this beach, some of which can be seen in the foreground of the beach photo. These have rolled down the cliffs from the conglomerate strata that jut out here. Stone 2 is a very small conglomerate stone, found on 20 September – and there are photos in the 20 September Post showing the cliffs.

This is a “polymictic” conglomerate, where the clasts have come from more than one rock type – see Alex Strekeisen‘s description of types of conglomerate. In Stone 2, some of the tiniest clasts seem to be angular, not rounded like the larger ones. As far as tumble polishing goes, it may turn out that the clasts are not well enough cemented to survive much tumbling, and tiny fragments may fall out of it.

August’s Stone 3 was my most intriguing find of 2024. I could tell when I found it on 20 September that it has interesting little bits inside it but it wasn’t until I photographed it that a wondrous sight presented itself.

It looks like the stone consists of hundreds of tiny fossils. The mushroom-like shapes in it (long stalks with a funnel at one end) especially caught my eye (see photos below). There appear to be bits and pieces of different white fossils there. I have not seen anything like this before.

I posted photos of Stone 3 on the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, asking if anyone could identify it. Most people did not know what it might be, though one person made a very helpful suggestion: “It looks to be agatized forest floor – composed of leaf litter, stems, and small bits of wood.” That seemed reasonable to me. Jocelyn Thornton, on page 24 of “Gemstones” , presents a stone that she describes as follows: “Peat or other plant debris may be preserved in silica. The example is a chunk of stems, roots, leaves, and so on from Southland, where this material is called ‘forest floor’.” I think I have seen such stones before, but they have not had the strange features within them as are present in Stone 3. Nevertheless, in the early printing runs of the Calendar, I labelled Stone 3 as “Agatised Forest Floor?”

Then, while writing up the description of May’s Stone 3 from Ward Beach, I followed up a suggestion by “Kween Bee”, in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, that the tiny elongated features in it could be fossil sponge spicules. What are spicules? The 2017 NIWA publication “Splendid Sponges” states on page 4: “Most sponges produce a skeleton of fibre made from a special collagen called spongin, which may or may not contain sand grains or spicules. Spicules are siliceous elements made by the sponge that come in an amazing array of forms and are usually used to identify the species. Some sponges have only spicules and no spongin.” As Wikipedia puts it: “Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge’s skeleton and thus it provides structural support and potentially defense against predators.” There are three major groups of sponges, some of which have calcium carbonate spicules (Class Calcarea, currently rare in New Zealand), and some of which have silica spicules (Class Hexactinellida and Class Demospongiae). I decided that I couldn’t really find any spicules similar to what is in May’s Stone 3 from Ward Beach, but then I wondered whether they might be relevant to August’s Stone 3 from Slope Point. I found a couple of diagrams of spicules in Wikipedia which didn’t show anything similar to Stone 3’s long-stalked mushroom-like shapes (see first two diagrams below). Then I came across an academic article in “Aquatic Biology” in 2020 in which a diagram of spicules showed something similar to Stone 3’s feature (see third diagram below).

The spicule labelled B in this third diagram comes from a sponge called “Acalle recurvata” which is to be found in the Amazon River in Brazil. That’s a long way from Slope Point and it’s not a fossil. But I find it suggestive that maybe Stone 3 contains fossil spicules of some kind. So in the later versions of the Calendar, Stone 3 is labelled “Fossil sponge spicules?” and some more research sometime is in order.

Stone 4 is a kind of spherulitic (or orbicular) rhyolite that I found on this Slope Point beach on 2 March.

These are not common and are keenly sought after. I have found maybe three or four. The circular features in the stone are cross-sections through small spheres with a radiating structure that have formed in the rhyolite. In “Some More Recently Polished Stones from Slope Point and Kakanui”, the second stone is a slightly different spherulitic rhyolite in which radiating arms are apparent. These are sometimes called chysanthemum rhyolites because of their flower-like appearance. Alex Strekeisen writes: “Spherulites are typically two-mineral aggregates (mainly quartz and feldspar), formed by initial spherulitic growth of one mineral and later crystallization of a second mineral from the liquid or glass between the fibres.” Gordon Sherwood (New Zealand Rocks Downunder) has a YouTube video of hunting for spherulitic rhyolite near Waihi. From 9 minutes 9 seconds in the video, he shows some good specimens in the rough.

The months of September (Gemstone Beach) and October (Ward Beach) in the 2025 TumbleStone Calendar are featured here. This 2025 Calendar is for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.

The 2025 TumbleStone Calendar features beach stones collected during my two South Island fossicking trips in 2024. Details about the stones shown in the months of January and February are here and for the months of March and April are here. The month of May is the first of two months featuring Ward Beach in Marlborough (the other month is October). June focuses on Kakanui’s Seadown Beach (which we first met back in March). Note that the stones in the Calendar were photographed in the rough while wet, held in my hand in bright sunlight. The photos often reveal more about the stones than I noticed on the beach. My identifications are often missing or tentative, and should not be relied on unless previous Blog Posts provide good evidence for them.

MAY – WARD BEACH

May’s photo of Ward Beach was taken at low tide, looking northwest towards the carpark. When the tide comes in, the rocks in the foreground become completely covered. I took the photo when visiting the beach on 2 October, on my way home at the end of my second fossicking trip for the year. I found Stones 3 and 4 below on that day. Ward Beach is about six kilometres off the main road east 0f the small village of Ward in Marlborough, 82 kilometres north of Kaikoura and 45 kilometres south of Blenheim. I had two fossicks that day and the photo was taken at 10 in the morning when the tide was low.

The first Ward Beach stone for May is what I think could be a veined limestone pebble with some brecciation. Often the veins are bright white, as in this one, found on my way south early in September.

I wonder if the brown bits in the stone might be flint. A wide range of types and colours of limestone can be found on Ward Beach, many of them veined and/or brecciated, some with flint inclusions. See, for example, the Series “Selection of Tumbled Ward Beach Stones”, where Part 2 features “Limestone Pebbles” and Part 3 “Stones With Veins”. In Thornton’s “Gemstones”, page 31 “Beach pebbles – East Coast from Hawke Bay to North Canterbury”, there are specimens of such limestone.

May’s Stone 2 is most likely a jasper, found on 25 March, the final fossick of my first trip. This year, I have started to pay more attention to the red jaspers on Ward Beach.

The printing of the Calendar makes this stone look red when, as you can probably see here, it actually has an orange tinge (at least, it does to my eye). When I noticed this, I double-checked what photo I had used, and confirmed that it had turned out differently. This is the only case where it appears the printing process has significantly changed the colour of a stone in the 2025 Calendar. I have not struck this before.

Stone 3 is my most exciting find on Ward Beach so far, though I am struggling to identify it. It may not be a good candidate for tumble polishing but it has fascinating detail in it. I found it on 2 October, the last fossick of the year. What caught my eye were what I thought were the elongated crystals within it.

“Acicular” crystals are thin and needle-like, either tapering to a point or having a blunt termination. A “prismatic” crystal habit is pencil-like, with elongated crystals that are thicker than needles (for more on crystal shapes and habits see Geology.com and Wikipedia). So I initially thought the small long features in Stone 3 could be crystals, maybe small prismatic ones. However, when I posted photos of the stone on the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, it was suggested that these were not crystals but fossils, maybe sponge spicules. I have just done some research on spicules and am not convinced that is what we can see in this stone. Most spicules have a more complex character, and the rare long thin ones are said to come to a point. However, I have realised that another stone in the Calendar, August’s Stone 3, could contain fossil sponge spicules. So I will go into more detail about them when dealing with that stone in the next Post. In the meantime, May’s Stone 3 (above) remains a mystery. NOTE: 12 November 2024 – John Taylor, a rockhound and fossil enthusiast who lives in Scotland, visited me today and we discussed this stone. John looked closely at it under a magnifying glass and with a blacklight torch. The latter revealed some calcite present, and John thought the stone was most likely a shell fossil, probably of an oyster of some kind. The long thin features that had caught my eye are part of the shell material remaining after some erosion. Thanks, John!

My guess is that Stone 4 (below) is a brecciated flint. I am not confident in this identification as I don’t often visit Ward Beach, only once or twice each trip, and I am not yet very familiar with many of its stones. However it is clear that tectonic stress has partly crumbled this rock, giving rise to small fragments and opening up veins. It appears the veins are filled with a translucent mineral as you can see the brecciated material through them. In one vein, the internal surface of the grey material seems to have some white mineral over it, as a sheet-like coating.

Flint is a sedimentary cryptocrystalline form of quartz, closely related to jasper and chert. In other words, quartz has been put under pressure and heat to the extent that the crystals become too small to be recognised and separately distinguished even under an ordinary microscope. “New Zealand Geology, An Illustrated Guide” by Peter Ballance (2017), an excellent e-book freely available online, has a map of the Kaikoura Ranges on page 247. The map shows the distribution of “Amuri limestone and associated flints” aged between 25 and 65 million years. There is a section of this limestone at the coast just near Ward Beach (just south of Chancet Rocks on the map, below centre).

Ballance writes on page 248: “Cover strata in Marlborough include a prominent fine-grained white limestone (really a hard chalk) called the Amuri Limestone. It originated as a deep-sea calcareous ooze on the continental slope of the time, 65–25 myr ago, during phase three of New Zealand’s formation. Like its English equivalent in the White Cliffs of Dover, it contains nodules of dark grey chert or flint, made of fine-grained silica.” In a couple of past visits to the south of England, I got used to seeing flint on beaches there, such as at Slapton Sands. I even have a piece of flint I found near Grime’s Graves, a Neolithic flint mining complex in Norfolk. 

JUNE – SEADOWN BEACH, KAKANUI

June’s beach scene of Seadown Beach (below, left) was photographed on 5 September 2024, on my way south. I had two fossicks that day and the photo was taken when I first arrived there, just before 10 in the morning when the tide was low.

The first stone for the month of June was found on Seadown Beach on 23 March, during a two hour fossick on a foggy morning.

The stone is most likely a quartzite which is common on this beach. However, what is most interesting about the stone are the veins in it. Not only are they in an interesting arrangement, dividing the stone into three sections, but they appear to have chalcedony (agate) in them. This is suggested by the thin white traces that become clear in the close-up images.

June’s Stone 2 is an interesting mish-mash of bits and pieces. It is a fossilised piece of ancient seafloor which I found in the afternoon of 30 September, a day on which I had two fossicks on Seadown Beach.

The two larger spherical features within the stone are fossil rhodoliths. Rhodoliths are marine nodules of algae made up mainly of calcium carbonate, and they can accumulate on the sea floor to resemble beds of coral. My research has shown that fossil rhodoliths are known to be present in the North Otago region. See TumbleStone Blog’s “Fossil Rhodoliths and Farewell to Kakanui’s Seadown Beach” for more information. The stone will be relatively soft, not unlike limestone, and so won’t polish in a tumbler.

Seadown Beach has a wide range of interesting jaspers (for example, see the four at the beginning and the one at the end of this Post and the nine in the middle of this Post). Stone 3 for June is a dark red jasper, though it lacks the hematite that would intensify its colour. I found it on the morning of 30 September.

This jasper has been brecciated by tectonic stress, the forces of the earth’s movement. Then it got into hot water. This hot water flowed through the gaps and fragments and veins and left behind the mineral silica. The silica was in a dissolved form in the hot water then precipitated out when it cooled.

I found Stone 4 during the same fossick that produced Stone 2, in the afternoon of 30 September. That day I wrote: “The most unusual stone stone I found this afternoon was this small dotted one, a type I have not seen before.”

It is a similar colour to a number of types of stones I have found on Seadown Beach, including quartzites, but I have not seen this pattern of dots in a stone from here before. I can compare it to Gemstone Beach’s poppy jaspers (see July Stone 4) and spotted argillites (see Stones Gn21, 23 & 27 here), but it is not one of those. Another mystery, for the present.

The months of July (Slope Point) and August (Gemstone Beach) in the 2025 TumbleStone Calendar are featured here. These 2025 Calendars are for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.

The Introduction to this Calendar can be found here. The Calendar features beach stones collected during my two South Island fossicking trips in 2024. The stones shown in the months of January and February are described here. The month of March features Seadown Beach, Kakanui, which lies just south of the city of Oamaru in North Otago. April takes us back to Orepuki’s Gemstone Beach in Southland. Note that the stones in the Calendar were photographed in the rough and while wet, being held in my hand in bright sunlight. The photos often reveal more about the stones than I noticed on the beach. While none of eight stones below are labelled “unknown”, two of them have question marks after them. It is wise to take my identifications as those of an amateur tumble-polisher, I am not a geologist nor do I have the scientific means to confirm a stone’s character. My research and understanding are distinctly limited and ongoing.

MARCH – SEADOWN BEACH, KAKANUI

March’s beach scene of Seadown Beach (below, left) was photographed on 5 September 2024, on my way south. I had two fossicks that day and the photo was taken at 10 in the morning when the tide was low.

The first Seadown Beach stone for March is a quartzite. There are many yellow quartzites on this beach, some with a dash of red in them. But there are quite a few quartzites of pastel shades as well, mainly blue and grey. This find is maybe the best I have seen here of this latter type.

The stone was found on 30 September 2024, on my way back north. The TumbleStone Blog Post for that afternoon’s two-hour fossick was entitled “High Tide and A Few More Stones at Kakanui’s Seadown Beach”. Yellow, blue, grey and green quartzites are not uncommon on beaches in Otago and Canterbury, and I have found them, for example, further north at Birdlings Flat near Christchurch (see this 2016 Post, written before I knew much about quartzites). Quartzite is a term often used for a metamorphosed sandstone. In her booklet “Gemstones”, the geologist Jocelyn Thornton states on page 20: “Quartz sands cemented by silica make an extremely hard and durable quartzite which is found on some hillsides in Central Otago and washed down rivers and out along the coasts. These quartzites have cloudy patterns and take a very good polish.” More information on these stones can be found in the entry for Wednesday 26 May 2021 in this Post. Stone 3 below is also a quartzite.

March’s Stone 2 caught my eye because it is pink. If I saw it on Gemstone Beach rather than Seadown Beach, I would initially think it likely to be thulite (see April’s Stone 4 below). However, upon closely inspecting this stone, it looked and felt more like limestone, or something very like it. Limestone is well known in the North Otago area but it is usually whitish or cream-coloured.

As Te Ara The Encyclopedia of New Zealand states: “Limestone, a sedimentary rock abundant in New Zealand, consists mainly of the bones and shells of tiny marine fossils made of lime (calcium carbonate). Rocks with more than 50% calcium carbonate are considered to be limestone.” Also see University of Auckland Geology for basic information on limestone. March’s Stone 2 will be a relatively soft stone and won’t stand up to much tumbling – a light tumble in a fine grit will be all it needs to brighten it up a little. I found it on Seadown Beach on 6 September.

Stone 3 this month is another quartzite, but unlike Stone 1 it is a variety of the yellow ones on Seadown Beach. I found it the same day I found Stone 2.

The Blog Post from my fossick that day, 6 September 2024, features the wide range of Seadown Beach’s yellow quartzites. I wrote: “A type of stone that particularly stood out on the beach this morning was the yellow quartzite that can often be found here. I collected a few, always finding them hard to resist. Here are 20 of my quartzite finds… These specimens illustrate only part of the many variations of this type of stone. All of these have tiny quartz crystals in them.”

March’s Stone 4 is the most amazing stone I have found on Seadown Beach, just coming ahead of the bryozoan fossil stones from there (one of which features in the Calendar’s month of November). I found it on the afternoon of 2 September, during a 90 minute fossick. I was looking among stones right at the south end of the beach, in a tiny bay flanked by high rocks, when I spotted it.

It has been suggested by members of the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils” that it is agatised fossil bone. After some research, I have found a few photos on the internet of agatised dinosaur bone (see photos below) that have a lot of similarities – see, for example, Geologyin and Grafphoto.

I am not suggesting my Kakanui find is a dinosaur fossil but it definitely looks like agatised bone. A few days after writing this, on 7 November, I came across Thornton’s two specimens of fossil bone on page 25 of “Gemstones”. One of these has some resemblance to Stone 4, though Thornton’s photo is not very clear. She notes that some agatised fossil bones from Oaro (North Canterbury) are “from marine reptiles related to the dinosaurs and are about 70 million years old.”

APRIL – GEMSTONE BEACH

April is the second of five times that Gemstone Beach appears in the Calendar – it is the beach I visit most often. On 7 March, I spent five hours on the Te Waewae Bay coast, starting at Gemstone Beach. It was an especially windy day. Early on, I climbed a hill above the Taunoa Stream and took this photo (see below, left). It shows the eastern sweep of Te Waewae Bay with Monkey Island in the far distance and Pahia Hill in the background. The roof of the beach’s half-hidden house can only just be glimpsed centre left in the photo, on the other side of the Taunoa Stream. The two people on the beach in the middle distance are in front of the carpark.

The first stone that appears in April in the 2025 Calendar, at the top left of the page, is an amygdaloidal stone, sometimes known as a stone with “infilled volcanic bubbles”. I found it during a four hour fossick on 14 September.

I explain this type of stone as follows in the Post “Gemstone Beach and its Stones: An Introduction for the Passing Motorist – Part Six-B, Stones with White Spots & Crystals”: “Molten magma often contains dissolved gas which can form bubbles in the rock as the pressure is released on eruption. These bubbles can get trapped in the solidified rock, forming tiny holes (called “vesicles”). These holes then fill with mineral-rich fluids which leave behind deposits of minerals such as quartz, chalcedony (agate), calcite and zeolites – zeolites are a group of minerals with a crystalline structure made up of silicon, aluminum, and oxygen. The resultant ‘spots’ are called ‘amygdales’ (or ‘amygdules’), a term that comes from the Latin and Greek words for almond, reflecting the almond-shape of many such in-filled vesicles. However, many amygdales are round and others can be irregular shapes.”

April’s Stone 2 is the distinctive pistachio green of the mineral epidote. In New Zealand, epidote is widespread in veins in greywacke, schist and granite and is the main mineral in the iron-rich mudstones of Otago and Southland, including the argillite common on Gemstone Beach. See near the beginning of “Gemstone Beach and its Stones: An Introduction for the Passing Motorist – Part Seven-A, Green Argillite Stones” for more on epidote. In argillite, epidote is usually dispersed throughout the stone, giving it a uniform green colour – in Stone 2, it appears in small clumps, almost in an orbicular fashion.

I found this stone on 9 March. It is unusual for the intensity of the epidote in it.

Jasper can be found in many places in New Zealand. Along with chert and flint, it is a variety of opaque microcrystalline quartz. It can be a number of colours, dark red the most common but green and yellow also often found. There’s more information and specimens on pages 17 and 18 of Jocelyn Thornton’s “Gemstones”. Sometimes jasper can have a mossy character, like April’s Stone 3.

This stone also contains white quartz. I found it on Gemstone Beach on 7 March, the same day I took the beach scene photo for the month.

April’s Stone 4 is thulite, a pink stone. I found it on 8 September, the first fossick on Gemstone Beach for that trip, three hours on a cold Sunday morning, but a very productive time.

There are clouds of intense bright pink in this stone – some thulites are much lighter in colour, like this one found in June 2021. In my experience, many of the brighter stones don’t tumble-polish well, coming out rough and non-shiny, while the lighter coloured ones often come out much better. Thulite is the pink to reddish variety of the mineral zoisite. As  Minerals.net  reports, “The color of thulite is caused by the element manganese in its composition. Thulite often occurs associated with quartz, and is sometimes mottled with streaks or spots of white quartz.” Thulite is the national gemstone of Norway. You can read more about it on Wikipedia and Gem Adventurer.   

The months of May (Ward Beach) and June (Seadown Beach, Kakanui) in the 2025 TumbleStone Calendar are featured in the next Post. These 2025 Calendars are for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.

The Introduction to this Calendar can be found here. The Calendar features beach stones collected during my two South Island fossicking trips in 2024. The month of January features Gemstone Beach, on the south coast of Southland, along with four stones I found there in 2024. February takes us 140 kilometres west to Slope Point, in the Catlins District, also in Southland.

Note that the stones in the Calendar were photographed in the rough and while wet, being held in my hand in bright sunlight. So this is how I first saw them on the beach. However, the photos often reveal details not initially grasped. Three of the eight stones below are labelled “unknown”. My identifications for others include tentative suggestions – my research and understanding are ongoing.

JANUARY – GEMSTONE BEACH

January’s scene of Gemstone Beach (below, left) was photographed on 6 March 2024. The previous day had been quite stormy, and snow appeared on the tops of the mountains in the distance. I took the photo of people looking for stones in front of the carpark just as I was leaving the beach after a three hour fossick. The TumbleStone Blog Post for that day was entitled “Another Post-Storm Fossick Finding Treasures on Gemstone Beach”.

The first stone that appears in January in the Calendar, at the top left of the page, is an “unknown” one. I found it on 12 March during a fossick that included encounters and conversations with a number of people on Gemstone Beach – see “With Claire and Brett on Gemstone Beach”.

I really like the contrasting light and dark areas in this stone as well as, unusually, the diffuse nature of the patterning. This is unusual in that I generally seek out stones with well-defined tiny details. The lighter material in it could be quartz or quartz-derived, with maybe epidote providing a tiny tinge of green here and there. I don’t know what the black mineral is. It’s always nice to be able to identify a stone but the lack of an identification does not detract from its attractiveness.

January’s second stone, top centre of the page, was an exciting find. It was also found in March this year, just a couple of days before Stone 1 – see “Sunday Afternoon Fossick, Gemstone Beach and Te Waewae Bay”. I was immediately attracted by the bright intense green within the stone.

Closer inspection also reveals some intriguing white “swirls” in the lower part of the stone. I posted a photo of a similar find in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, asking if anyone could identify it. Someone from Nelson responded – rocks in the Southland area and Nelson area are often similar as they were originally connected prior to the Alpine Fault tearing them apart. He commented that it looked a lot like the chromium in diopside in semi-nephrite he knew from his local region. Also called “chrome diopside”, the mineral is a vibrant green variety of diopside coloured by chromium – see Mindat here and here. I have no experience of semi-nephrite, though it is mentioned as present on Gemstone Beach. I have tended to think of semi-nephrite as dark in colour and initially wondered whether the white part of this stone might actually be hydrogrossular garnet. However, I have recently come to understand that nephrite and semi-nephrite can be white – here are three examples of spots of chrome diopside in nephrite, carvings by Wayne Costar that he had posted on Instagram. The second of these has significant white in it.

Another example of chrome diopside in white nephrite can be found here. Nephrite is not found on Gemstone Beach but semi-nephrite is sometimes mentioned as present there. This example of a Gemstone Beach semi-nephrite is a light green colour. Semi-nephrite, as one source puts it, is a low-grade form of nephrite. In other words, it is a rock that is on its way to becoming nephrite but is not quite there in terms of mineral structure. Semi-nephrite is dominated by large tremolite mineral crystals, which occur within a mass of smaller crystals. These differing crystal sizes create a structural weakness that contrasts with high-grade nephrite, which is very strong. It is not beyond the realms of possibility that January’s Stone 2 is semi-nephrite.

January’s third stone is a poppy jasper, also known as orbicular jasper. The size of the orbs in poppy jaspers range from tiny to large – this stone has orbs of the larger variety (July’s poppy jasper has much smaller orbs). You can also see hematite, a grey metallic mineral, in the stone – its presence always seems to intensify jasper’s deep red colours.

One of the stones I found on the day that the photo of the month’s beach scene was taken is the fourth stone for January – the jasper on the lower right of the page. See the Blog Post “Another Post-Storm Fossick Finding Treasures on Gemstone Beach”. I found the stone in an area I don’t often visit, just to the left (eastwards) of the carpark, on the other side of The Steam With No Name. I remember it was amazingly smooth and its clear vein caught my eye along with the patches of metallic hematite and the flowing lines of contrasting dark and light.

The stone appears to have come under tectonic stress, causing some brecciation and creating openings for the clear silica to enter. I have now tumble-polished it and it is outstanding, looking very similar but bright and clear.

FEBRUARY – SLOPE POINT

February’s beach is at the head of a small bay, just under two kilometres east of Slope Point, the southernmost tip of the South Island. I visited there on 2 March 2024, accompanied by Chrissy Lampitt who can be seen in the beach photo (below, left). The TumbleStone Blog Post for that day was entitled simply “A Sunny Slope Point Fossick”. A more detailed introduction to the beach is provided in a Post about a fossick there in March 2023, “Journeying to a Slope Point Beach”.

The first stone that appears in February in the 2025 Calendar, at the top left of the page, is an “unknown” one. It is primarily black, and appears to have some light-coloured orbs in it.

It was found on this beach on 13 March 2024, along with this month’s Stone 3. Another type of orbed stone, spherical or chrysanthemum rhyolite, can also be found here – see this Post for examples, and August’s Stone 4.

20 November: Stone 2 has just been tumble polished, and I’m not sure it has been improved, except for now being permanently shiny. Some orbs have lost their centre dot, though some other light-coloured features have made their appearance.

February’s Stone 2 is a breccia, found on 20 September. Breccia of various kinds are present on this beach.

As I note in a previous Post, in “breccia”, the fragments (or “clasts”) that make up the stone have not travelled far before being cemented together and so are angular and sharp. In a “conglomerate”, the fragments have undergone some rounding from the travel they have experienced, usually from water, prior to being cemented together. Sometimes, a brecciated stone is caused when massive stresses on a rock tears fragments from it which are then cemented in a matrix – this is often known as “tectonic” breccia. Other times, “sedimentary” breccia occurs, when fragments from different stones end up cemented together in a fine-grained matrix. A third main type is “igneous” breccia, where the clasts consist of pyroclastic debris ejected by a volcanic blast or pyroclastic flow. It is known that some Slope Point stones have arisen from Jurassic Era volcanic activity and debris flows, so I suspect Stone 2 is volcanic breccia. It is also “polymictic”, a breccia where the fragments or clasts come from more than one rock type.

Stone 3 is my most prized find from my four fossicks on this Slope Point beach this year. It is my first piece of petrified fern. In my Post on my 13 March visit, “Second Slope Point Fossick”, I described its discovery as follows: “I was sitting on a rock, resting before leaving the beach to tackle the steep climb back to my car, (when) the edge of a dry stone with squiggles in it caught my eye.”

In her booklet, “Gemstones” Jocelyn Thornton writes on the pebbles to be found at Slope Point (page 35): “The prize is petrified punga, found as black nodules barely showing the eyed grain of the fern.” The grain in this stone is much clearer. It is currently in the tumble polisher.

20 November: Stone 3 is now polished. There are two or three small rough areas on the surface but I didn’t want to tumble it longer to fix those as it would just make the end product smaller.

The surface of the stone has changed quite a bit due to the tumbling. For example, one area of the stone has an oval feature with a squiggly oval in the centre. The tumbling has removed the squiggly centre:

Stones with detailed features in them are at risk of such changes in tumble polishing.

February’s Stone 4 is another “unknown”, found on 2 March.

Its light colour caught my eye initially, then I noticed that it appears to contain a range of different crystals.

March (Seadown Beach, Kakanui) and April (Gemstone Beach) in the Calendar are featured in the next Post. These 2025 Calendars are for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.