Category: Gemstone Beach, Orepuki

March 2026 Stone Collecting Trip – Part 11, Maybe an Agate, and Maybe a Large Rhodonite, Gemstone Beach, Thursday 26 March

This is my fourth and final visit to Gemstone Beach for this trip. Chrissy and I arrived there around 2pm, just after low tide. There were quite a few people here today – there were two campervans and six cars in the carpark when we arrived. Again the beach was very sandy, though there was a good scattering of stones along the wave edge in front of the carpark.

In front of the carpark.
Two horses and a dog by the Taunoa Stream.

We made our way down to the far (northwestern) end of the Waimeamea River lagoon before turning back just after 3.30pm. Tiring from a heavy load of finds, we made it back to the car an hour later. We saw a lot fewer trace fossil stones than previously, and hydrogrossular garnets were still few and far between.

Looking back at a bunch of people in front of the carpark.
Chrissy by a seepage in front of the Waimeamea River lagoon.
It was here, down at the Waimeamea River lagoon., that I found a large pink stone.

Because of the cloudy weather we’re having, I was unable to take photos of my finds until two days later – and even then, the light conditions were challenging. The images of stones below reflect those difficulties.

One of my most intriguing and enigmatic finds today was made early on in front of the carpark. It kind of looks like quartz, which is what I expected it to be. But it kind of looks like chalcedony (agate) too. After careful examination, and seeing it both wet and dry, I’m leaning towards chalcedony. But this is a very rare find along this coast, as far as I know, and I have found only one like it last August at McCracken’s Rest.

Looking a bit like quartz when wet.
Looks more like an agate when dry.
Dry view of the “top”.
Wgen held up to the light.

The largest of my finds today also poses an identification question. This large pink stone appeared in front of me down near the Waimeamea River lagoon:

The pink side of the large pink stone.
Some dark mineral apparent in this side.

The first side (above) was showing when I found it – it is completely pink, so I thought “thulite”. Turning it over, however, there is some dark mineral in it, maybe an oxide, that makes the stone look like “rhodonite”. I’m leaning towards the latter ID, on the basis of the visual evidence.

A little later on, I found a much smaller version of a similar stone with a similar question about it, and interestingly it contains some brecciation:

Small pink stone with some brecciation.
Other side, with some dark material.

I found four stones this afternoon that are or could be poppy jaspers. The first three definitely are:

Poppy jasper #1.
Poppy jasper #2.
One side of poppy jasper #2.
Poppy jasper #3.

The fourth one is more cryptic – the orbs are not clear but there are hints of them here and there:

Some orbicular features in this jasper.
Other side of stone.

Four different kinds of quartzites (maybe) I found today – the first is green, the second is red, the third is more subdued in colour but is not unlike some I have found at Kakanui, and the fourth I am least sure about because it has larger fragments of material in it than usual:

Green quartzite.
Red quartzite.
Different kind of quartzite.
Quartzite? Certainly epidote is present.

Three orange stones, no doubt coloured by the presence of iron oxide:

Small bright orange stone.
A type of quartz , with a white end.

Finally, the only interesting hydrogrossular garnet I found this afternoon:

Hydrogrossular garnet.

My next fossick will be at Riverton Aparima. An Index to this Series is here.

March 2026 Stone Collecting Trip – Part 10, A Foggy Start to a Gemstone Beach Fossick, Wednesday 25 March

When I arrived at Gemstone Beach for a solo fossick at 10am, there was a lot of fog along the coast, and the temperature was 12 degrees. That eventually lifted after about 45 minutes. I spent two and three-quarter hours on the beach, by which time the sun had raised the temperature to 17 degrees.

Fog on Gemstone Beach, looking towards Fiordland.
Looking towards Monkey Island.
The large patch of stones just over the Taunoa Stream.
After I had made my way down the beach, the fog started to lift.

I chatted with a number of people picking up stones – some were from overseas and some were locals. They included a young couple who live in Wellington though they come from Scotland, an older couple from Cromwell, and two women from the United States, friends of Chrissy’s. Sometimes they showed me their stones and I talked about their identification, and sometimes they asked what I had found. I probably talked to eight of the 12 people there. The tide was low this morning and there was still a lot of sand on the beach. Just over the Taunoa Stream was a large patch of stones that people tended to spend time at. I walked down to the Waimeamea River which has been blocked from running to the sea – the waves had piled up stones there. Some seepages had formed as the water made it way in places through the stones.

The stones (and sand) just before reaching the Waimeamea River.
Seepages of water emerging from the stones in front of the Waimeamea River lagoon.
Seepages.
The bank of stones down near the Waimeamea River lagoon.
This is where the Waimeamea River was flowing, when I was here six days ago.
The Stream with no Name, near the carpark, was flowing very low and disappearing into the sand before reaching the sea.

Fourteen of my finds are featured below. The first is the largest hydrogrossular garnet I have found so far on this trip – these have not been showing up at all except for the very occasional quite small one. I found this large bashed-about garnet down near the Waimeamea River:

Hydrogrossular garnet.
Other side of hydrogrossular garnet.
It’s almost as if the garnet is wrapped around some black rock.

My most spectacular find this morning is another of those small jaspers that come to life with close-up photography. It proved difficult to get very clear images but the following give some idea of the amazing world in there:

Small jasper with amazing details.
Another side of the small jasper.
Slightly different view of small jasper.
The “bottom” of the small jasper.

It almost looks as if a tiny pen has made a tracery of lines and filled in patches – and the small white areas are attention-grabbing.

Next is another small red jasper (I found a couple more as well). In this one, the tiny white circular patch just above centre caught my eye on the beach – but the photos reveal a lot more:

Another interesting small jasper.

Here are three argillite stones with trace fossils in them, illustrating the diversity that can be found on this beach:

Three different sizes and characters.
A busy group of trace fossils.
It was the small trace in the lower right that caught my eye.
Well-defined traces in a small argillite stone.

An amygdaloidal stone with some bright red amygdales:

Amygdaloidal stone.

Amygdaloidal stones are also known locally as volcanic bubble-infilled stones. They originate in molten magma which may contain dissolved gas that forms bubbles in the rock. These tiny bubble holes then fill with mineral-rich fluids which leave behind deposits of minerals such as quartz, chalcedony, calcite and zeolites. The resultant “spots” are called “amygdales” (also “amygdules”), coming from the Latin and Greek words for almond, reflecting the almond-shape of many such in-filled holes. However, amygdales can also be round and some can be irregular shapes. Further Gemstone Beach amygdaloidal stones can be seen in this Post, Section 4, Stones W30 to W42.

A small stone with a very busy composition – it looks like a polymictic breccia, a stone full of tiny angular fragments from a variety of sources, some of which look to be mudstone/argillite:

A small breccia?
Other side of stone.

Next are five of this afternoon’s finds where the predominant colour is green, most often due to the presence of epidote – the first two and fourth are probably quartzite, some have quartz veins or patches, and some brecciation can be seen at times:

Quartzite.
Another quartzite.
Not sure what this is.
A very light green stone.
Some brecciation in this stone.

Finally a grey stone with tiny black and white crystals and/or fragments:

A severe storm is heading our way, bringing heavy rain and strong winds over the next few days. Some parts of New Zealand are under a Red Warning – significant impacts and disruption are expected. The stormy waves will stir the beach stones up (and move sand around) but may make fossicking uncomfortable.

“There’s A Storm A-Coming”
by Richard Hawley

There’s a storm a-coming, you’d better run
There’s a storm coming, goodbye to the sun
There’s a storm a-coming, you’d better run boy run
You’d better run

There’s a ship that’s sailing out in the night
There’s a heart that’s breaking, I think it’s mine
There’s a storm a-coming, you’d better run boy run
You’d better run

Every little part of you is a miracle of molecules
Every little thing you do so sad, in the end
Oh, in the end

There’s a ship that’s sailing out in the night
There’s a heart that’s breaking – I think it’s mine
There’s a storm a-coming, you’d better run boy run
You’d better run

The next Post in this Series is my fourth and final visit to Gemstone Beach on this trip. An Index to the Series is here.

March 2026 Stone Collecting Trip – Part 7, Second Visit to a Sandy Gemstone Beach, Thursday 19 March

Chrissy and I visited Gemstone Beach again, arriving just after 3pm, leaving around 5.30pm. It was cloudy, 14 degrees, with a light breeze, and the tide was going out. When we arrived, there were six cars and three campervans in the carpark. It was still a very sandy beach, like it was two days ago, but a couple more patches of stones had been exposed by the waves, one of them just over the Taunoa Stream. We walked down to the Waimeamea River again, this time fording it and spending maybe 15 minutes on the other side.

People on Gemstone Beach when we arrived.
A patch of stones on the other side of the Taunoa Stream.
Looking back towards the carpark.
The Waimeamea River, similar in flow to the Taunoa Stream today.

On our way back, just after recrossing the Waimeamea River, we stopped and chatted with Robyn and Judy who we also met two days ago.

Ten of my finds are featured below. The types of stones we saw on the beach this afternoon were similar to those we saw two days ago. There were very few hydrogrossular garnets and Chrissy found only one very small poppy jasper. Again, there were quite a few trace fossil stones. I did find a number of stones with interesting textures. The most intriguing has spots in it – which is why I spotted it – and the close-up photos suggest it is a spherulitic rhyolite. According to John Farndon’s (2015) book, “Illustrated Guide to Rocks & Minerals”, spherulitic rhyolite originates in “trapped gas pockets of volatile vapours” which develop into “balls of radiating needle-like crystals of quartz and feldspar” (page 64). 

Perhaps spherulitic rhyolite.
Other side of stone.

See Strekeisen for a relatively techical account of spherulites, along with some great photos and diagrams. This stone is only the fourth spherulitic rhyolite I have found on Gemstone Beach in nine years. In Southland, it is a type of stone much more associated with Slope Point.

Next are three stones with very interesting textures that become apparent in the close-up photos:

Interesting texture #1.
Interesting texture #2.
Interesting texture #3.

When I put stones like this in my bag, I don’t always know how they will look upon closer examination. These three proved to be worthwhile and intriguing specimens.

This afternoon’s best trace fossil stone was found by Chrissy who kindly gave to me, a grey argillite with clearly defined traces in it:

Traces fossils in argillite.
Other side of stone.

I found this unusual one myself – I’ve not see a trace fossil like this before:

Trace fossil in argillite.

I came across only one small nice hydrogrossular garnet, along with a handful of much smaller and much less interesting ones:

Hydrogrossular garnet.

A small colourful quartzy find – white with bright orange, and some brecciation:

Colourful find.
Slightly different perspective on this stone.

A veined green quartzite with a dark irregular central vertical band:

Quartzite.

Finally, I always like good specimens of black igneous stones with small white crystals (as in Section 5 in this Post), This find is one of the larger ones I have collected:

Black igneous stone with tiny white crystals.

Tomorrow I undertake a short fossick on Papatotara Beach. An Index to this Series is here.

March 2026 Stone Collecting Trip – Part 6, Lots of Sand on Gemstone Beach, Tuesday 17 March

I am staying with Chrissy and Mike, and Ohla the dog, at Papatotara, a few kilometres west of Orepuki’s Gemstone Beach. Today, Chrissy and I spent three hours there, on a cloudy afternoon with a light breeze, the temperature being around 16 to 17 degrees. There were four vehicles in the carpark when we arrived, with two more arriving just after we got there. The beach in front of the carpark was predominantly sand, with just a couple of patches of stones on either side of The Stream With No Name (marked as “Un-named Stream” on the map below – see this Post for more on the beach and its location).

Gemstone Beach. Source of base map = mapcarta.com
A sandy Gemstone Beach, looking north west.
Looking back towards the carpark.

You can always spot stones in the Taunoa Stream. Today it was running low and was easily searched and then forded.

Chrissy looking at stones in the bed of the Taunoa Stream.
Looking up the Taunoa Stream towards a recent new house.

Normally, masses of stones appear on the beach not far on the other side of the Taunoa, as you walk along the Te Waewae Bay coast, but that was not the case today. We struck more and even more sand for a few hundred metres, with only tiny patches of stones along the base of the cliff backing the beach. The large area of stones didn’t start until maybe three hundred metres before the Waimeamea River – see the description of “Section Three” in this Post for more about this 1.5 kilometre stretch of beach. (I’ve included Chrissy in some photos to provide a sense of scale – thanks to her for agreeing to this.)

For a long stretch of the beach, only small patches of stones at the base of cliffs.
Chrissy at the “cut” in the cliffs, which has had up to a metre of sand washed into it.
Exposed stones appeared as we got closer to the Waimeamea River mouth.

We decided to turn back at the Waimeamea River mouth. I think we could have forded it if we wanted to go further, but our backpacks were getting heavy.

The usual masses of stones, close to the Waimemea River lagoon.
Chrissy making her way slowly along the beach.
The mouth of the Waimeamea River. Not too deep today.
Bank of stones on left, dry Waimeamea River lagoon full of driftwood to the right.
The beginning of the wet Waimeamea River lagoon area, the river mouth is centre left.
Chrissy in the distance, looking for stones at the Waimeamea River mouth.
Te Waewae Bay waves.
Te Waewae Bay coast beach stones.
Te Waewae Bay coast beach stones.

It turned out that our backpacks became quite heavy. It was hard going trudging across the metres and metres of sand back to the carpark. When we got there, we met Robyn Bennett and her friend Judy. Robyn had messaged me about a week ago, having read TumbleStone Blog as well as some of my posts in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. She had told me they would be coming to Gemstone Beach at the beginning of this week, so it was good that we were all there at the same time. We had a good chat and showed each other some of our finds, as rockhounds do.

This afternoon’s fossick featured trace fossil stones – I kept on coming across them, and some were very good specimens or unusual for some reason. They made up maybe one-third of the stones I put in my bag. And Chrissy always gives me good ones she comes across. We saw very few hydrogrossular garnets and I found only one tiny poppy jasper. But there are always interesting stones that crop up when time is spent along this part of the Te Waewae Bay coast. Fourteen of my finds are featured below.

First, the big and the tiny. This is the largest of the trace fossil stones I collected, with the longest trace I have seen for some time. And following it is a tiny poppy jasper fragment I found, which still looks amazing in close-up:

Long trace fossil in argillite.
Tiny fragment of poppy jasper, with hematite.

Green stones can often be found on this beach. Two green-coloured stones I picked up, one light hued, one dark:

Complex structure and intense green veins.
Other side of stone.
Brecciated, black veins.
Other side of stone.

A pink find, most likely a rhodonite, similar to one featured in an August 2025 fossick:

Probably rhodonite.
Other side of stone.

This next stone is very unusual, with a mineral of light cream colour set in translucent quartz(?). In addition, there is a smearing of dark brown iron oxide across it:

Interesting colours and structure.
Other side of stone.

Another unusual stone, of mottled black and dark red:

Unusual mottling in this stone.

A stone with fragments of different colours, maybe a breccia?

Breccia?

Finally, six more trace fossil in argillite stones I collected today, showing some of the diversity of this type of stone – variations in colour of stone, colour of trace, and shape and size of trace:

Trace fossil in argillite, the most common green colour of host stone..
Grey trace fossil stone.
Light grey stone, very light grey traces.
Many tiny trace fossils.
Black argillite stone.
Trace fossils in a banded argillite?

Gemstone Beach and nearby Te Waewae Bay coast never disappoints me. I’ve always found at least one unusual and interesting stone, usually many more. Even if, as today, I have to walk a ways to find them.

The next Post in this Series reports on another visit to Gemstone Beach, two days later. An Index to this Series is here.

Z is for Zeolite

This is a slightly expanded version of my letter “Z” contribution to the current weekly Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “Z is for Zoomorphic Shape in Stone”.

Z is for Zeolite

Gemstone Beach basalt amygdaloidal stone, with zeolites.
Other side of stone.

This is an amygdaloidal stone (unpolished) I found on Gemstone Beach in August 2025. I have found similar ones there before – they are dark red, likely to be basalt, with “spots” of interesting colours. Here is a smaller tumble-polished specimen:

Small polished Gemstone Beach amygdaloidal stone.
Other side of stone.

The spots are in-filled gas bubbles and the infill is likely to be a zeolite mineral. 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, calcite and zeolites. The resulting in-filled holes are called “amygdales” or “amygdules” from the Latin and Greek words for almonds because of their often almond-like shape. However, amygdales can also be round and some can be irregular shapes, as can be seen in this Post’s two Gemstone Beach stones and the specimens below:

Specimen of amygdaloidal basalt. http://www.alexstrekeisen.it/english/vulc/amygdales.php
Specimen of amygdaloidal basalt. http://www.mindat.org/gm/50668
Specimen of amygdaloidal basalt. http://www.mindat.org/gm/50668
Specimen of amygdaloidal basalt. http://www.mindat.org/gm/50668
Specimen of amygdaloidal basalt. http://www.mindat.org/gm/50668

To get back to zeolite: In the 18th century, Swedish mineralogist Axel Fredrik Cronstedt first identified and named zeolites when he observed a group of minerals which released large amounts of steams when boiled – the name “zeolite” is derived from the Greek words “zeo”, to boil, and “lithos”, stone (Wikipedia and GeologyScience). There are more than 40 naturally occurring zeolite minerals, including natrolite, stilbite, phillipsite and heulandite. The zeolite wairakite (photo below) was first discovered and named in New Zealand in 1955 by Alfred Steiner, a pioneer geothermal scientist. He had found it while examining hydrothermally altered drill cores at Wairākei in the course of exploration for geothermal steam (Te Ara). It has subsequently been found worldwide.

Natrolite, a zeolite. https://en.wikipedia.org/wiki/Zeolite
Wairakite, a zeolite. http://www.mindat.org/min-4230.html
https://geologyscience.com/minerals/zeolite/

Zeolite minerals have a wide range of applications in diverse industries, thanks to their unique structural and chemical properties. Their ability to adsorb (to hold onto molecules as a thin film), exchange cations (positively charged particles), and act as molecular sieves has made them invaluable in many industrial and environmental processes, such as water purification and wastewater treatment. The letter “Z” featured below is formed by small thumb-nail size tumble-polished Gemstone Beach stones, including four red amygdaloidal stones.

Small polished Gemstone Beach stones.
Mainly trace fossils in argillite, a spotted argillite, others.
Rhyolite (lower), and hydrogrossular garnets (middle).
Jaspers, breccia, amygdaloidal stones, others.

That is the end of this Alphabetical Series. An Index for the Series is here.

X is for Xcellent Xample of an Xtrusive Igneous Stone

This is a slightly expanded version of my letter “X” contribution to the current weekly Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils” (though I seem to be the only one regularly participating now). In the 2021 version of this Series I posted “X is for X-Figures When Veins Cross in a Stone”. 

X is for Xcellent Xample of an Xtrusive Igneous Stone, a Post made on Xmas Eve

Gemstone Beach flow-banded rhyolite, an extrusive igneous stone.

This is an extrusive igneous stone, a rhyolite, that I found on Gemstone Beach, Southland, on 5 March this year. Extrusive rocks are volcanic – they have formed when molten magma breaches the surface of the Earth. Depending on the way that breaching occurs, rhyolite can form as pumice (from a gas-rich frothy material with lots of tiny holes), ignimbrite (from compressed layers of volcanic ash), obsidian (glass-like), flow-banded (from the slow, viscous movement of lava). Stones like this one look like they could be flow-banded.

Rhyolite is the most silica-rich of extrusive rocks. It is generally fine-grained in texture, but may be porphyritic, containing larger mineral crystals in an otherwise fine-grained material. The small light-coloured crystals in this stone illustrate that. The minerals that make up rhyolite are predominantly quartz, sanidine (a high temperature potassium feldspar), and plagioclase feldspar. It is the extrusive equivalent of granite. Granite is intrusive, forming beneath the Earth’s surface, having a similar mineral composition to rhyolite. However, some textbooks point out that rhyolite’s mica is black biotite and granite’s mica is muscovite, and rhyolite’s potassium feldspar sanidine is different from granite’s orthoclase.

I first learned to recognise rhyolite from spending time on Slope Point beaches with a local rockhound, Oliver. He showed me the difference between rhyolite and petrified wood – sometimes the fine-lined flow bands in rhyolite can look like the grain in petrified wood. After that, I began to recognise rhyolite stones on Gemstone Beach (see three further specimens below). In “Gemstones” (page 35), Jocelyn Thornton has a photo of 10 Slope Point rhyolites (see photo below, bottom row, right), one of which looks very similar to this one.

Another Gemstone Beach rhyolite, I think. Found September 2024.
Maybe a Gemstone Beach rhyolite? If so, it’s not flow-banded. Found March 2024.
The most common form of rhyolite found on Gemstone Beach. This one I found in April 2023.
Slope Point rhyolites – Page 35 of Jocelyn Thornton’s “Gemstones” http://www.onnaturesedge.co.nz/downloads/nzgemstones.pdf

For a tumble polisher like myself, the high silica content and often glassy nature of rhyolite mean it often polishes well, though the occasional tiny gas hole can interrupt the smooth surface. I have come across a small range of rhyolites on Gemstone Beach. I usually see one or two of this orange and brown flow-banded stone each fossick on Gemstone Beach but I have only collected a handful or so of the smoothest specimens.

The next Post in this Series is “Y is for YesterYear’s Yellows at Year End”. An Index for this Alphabetical Series is here.

V is for Veined Vein?

This is a slightly expanded version of my letter “V” contribution to the current weekly Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “V is for The Chevron Shape of Trace Fossils”. 

V is for Veined Vein?

Veined Gemstone Beach find.
A veined vein?

This is a Gemstone Beach stone I photographed in April 2023 when I was collecting images for use in the Series “Gemstone Beach and its Stones: An Introduction for the Passing Motorist” – it is Stone W92 in this Post. The stone has an untidy white vein (of quartz or calcite maybe?) running through the middle. And it looks like this vein itself has a thin brighter-white vein running through it. However, maybe the thin vein is a denser or more intense thread of the same mineral in the wider vein. Or maybe some tiny bubbles of water and/or air are present in that thin line, making it brighter. It is often hard to know what is going on in the stones we find.

Veins are a common yet fascinating feature in stones. This can be illustrated by three other Gemstone Beach finds that feature in the “Gemstone Beach and its Stones: An Introduction for the Passing Motorist” Series (see Stones W87, W103, W110 in this Post). In the first below, there are veins of different colours, thicknesses and direction. In the second are irregular opaque and transparent quartz veins. The third has cross-cutting veins:

Another Gemstone Beach find, probably argillite.
Very interesting texture to this stone.
Cross-cutting veins.

Veins are infilled cracks. When rock fractures due to pressure and stress, cracks of different sizes open up. This allows hydrothermal fluids, carrying dissolved minerals, to enter the gaps in the rock. Over time, the dissolved minerals precipitate out of the hot water. Crystals, such as quartz and calcite, grow within the cracks and fill them. Often, as the stresses on the rock change their orientation over time, veins will crosscut and even overlie each other, though veined veins are probably very rare. For a reasonably technical account of vein formation see Alex Strekeisen, with Wikipedia having a more easily read account. Note that, in contrast to a vein, a “band” is a layer that is an integral part of the original stone, such as a layer of differently coloured sediment in a sedimentary stone.

The next Post in this Series is “W is for Wacke”. An Index for this Alphabetical Series is here.

TumbleStone Calendar 2026: July – Trace Fossils in Argillite

The Introduction to this Calendar can be found here. 

July’s stones in the 2026 TumbleStone Calendar are five Gemstone Beach argillite pebbles with trace fossils in them. Locally they are often called fossil worm cast stones. Argillite is a sedimentary rock, a hardened slightly recrystallised mudstone. Along with greywacke, it comprises the basement rock of New Zealand. On Gemstone Beach, argillite stones are mainly green in colour but there are grey and red ones as well, with some banded argillites being brown. Examples of Gemstone Beach argillite stones can be found here. Trace fossils can be found in sedimentary rocks – they represent the movement and burrowing of animals across or through the sediments. A “trace” fossil is not a fossil of the animal itself but of something it has left behind. In the case of July’s trace fossils, the traces are a different colour than the surrounding rock because the burrows or trails have been infilled by different coloured and often finer-grained sediment. Some of the trace fossils in argillite on Gemstone Beach can be plain, short and straight but others can be sinuous and long, with lines of chevron shapes – this diversity can be seen in “The Tattooed Rock, The Trace Fossils… Revisiting Gemstone Beach’s Trace Fossil Stones”. The most interesting, to me, are the traces that fit into the protovirgularia grouping – see “Ichnogenus Protovirgularia and the Permian Rocks of the Eglinton Valley”.

Calendar Cover, 2026.
July.
July’s Argillite Stones with Trace Fossils.

Stone One (top row, left, in the Calendar) contains a number of trace fossils, the main one being a good example of a long sinuous protovirgularia trace made up of a number of chevron shapes:

Stone One, July.

The smaller roundish “spot” traces in the stone are likely to be end-on views of long traces – the burrow or trail is at right angles to the longer traces we see. I found Stone One on 25 March 2025 – it is a grey-green colour, not uncommon for trace fossil stones.

Stone Two (top row, right, in the Calendar) has a straighter protovirgularia trace in between two plainer ones which also have a hint of chevrons:

Stone Two, July.

Stone Two was found on 12 August 2025, and it is a lighter green than Stone One, again a common colour for Gemstone Beach’s trace fossil stones.

Stone Three (bottom row, left, in the Calendar) is a dark, almost black, argillite – the traces within it are a mix of black and light green, looking much like caterpillers crawling through it:

Stone Three, July.

I found Stone Three on 3 August 2025, the day I saw an aircraft land on the beach between Gemstone Beach and Monkey Island.

Unlike Stones One, Two and Three, Stone Four (bottom row, centre, in the Calendar) has a couple of trace fossils that are darker in colour than the surrounding rock:

Stone Five, July.

It looks like there are very tiny pieces of dark grit or fragments in the two central traces, giving them an unusual texture. I found a number of variations of trace fossil stones the day I found this one, on 21 August 2025.

Stone Five (bottom row, right, in the Calendar) is one of the more rare types, having red traces:

Stone Five, July.

Again, the trace belongs to the protovirgularia family. I found Stone Five on a bitterly cold day, on 27 September 2024, another good day for finding a variety of trace fossil stones on Gemstone Beach.

For August’s set of yellow stones, see this Post. 

TumbleStone Calendar 2026: June – Black & White Igneous

The Introduction to this Calendar can be found here. 

The month of June in the 2026 TumbleStone Calendar features six black and white stones, all found on the shores of Te Waewae Bay, Southland, five on Gemstone Beach and one a little further west on Papatotara Beach. These stones are all igneous. “Igneous” rock forms through the cooling and solidification of magma or lava. There are two kinds of igneous rocks. The first is “volcanic” (also called extrusive”), having come from volcanoes and therefore solidified relatively quickly. The second is “plutonic” (also called “intrusive”), having formed underground from molten magma and therefore solidified relatively slowly. The white in these igneous stones are crystals that have formed as the rock has cooled – the longer it takes for the rock to solidify and cool, the larger will be the crystals. I find it difficult to identify the type of rock each stone below comes from, and the identity of the white crystals likely varies from quartz to feldspar, among others. The black minerals could be hornblende or augite or even olivine. See the end of this Post for a slightly more detailed discussion on identification issues.

Calendar Cover, 2026.
June.
The black and white igneous stones of June.

I found Stone One (top row, left, in the Calendar) on 3 August 2025:

Stone One, June.

Along with Stone Three, it has the tiniest crystals of the six stones, although some of the white specks seem to be clusters of crystals.

Stone Two (top row, centre, in the Calendar) was found on Papatotara Beach on 16 August 2025:

Stone Two, June.

Its crystals are larger and more obviously rectangular, although again there seems to be a lot of clustering of them. They look to me to be plagioclase feldspar. A very similar stone has been labelled diorite in the collection board of long-time Gemstone Beach fossicker, Marion Troon, which featured in a Guardian article on the beach in September 2024:

Guardian article on Gemstone Beach http://www.theguardian.com/world/2024/sep/21/jasper-garnet-sometimes-sapphires-pocketfuls-of-treasure-at-gemstone-beach.
Guardian article http://www.theguardian.com/world/2024/sep/21/jasper-garnet-sometimes-sapphires-pocketfuls-of-treasure-at-gemstone-beach.
Diorite stone, Marion Troon’s board.

Stone Three (top row, right, in the Calendar), found on 12 March 2025, has a slight green tinge to it:

Stone Three, June.

There are some black areas in Stone Three as well as some very fine black veins. As in the other stones, close observation reveals that the crystals within it vary significantly in shape.

Stone Four (bottom row, left, in the Calendar), found on 1 August 2025, has, along with Stone Six, the largest of the crystals:

Stone Four, June.

However, there are a range of crystal sizes in Stone Four, some being quite small, and again there is a diversity of crystal shapes. from square to triangular to rectangular to circular.

Stone Five (bottom row, centre, in the Calendar) has an unusal “smear” that runs from its middle to the lower right, a distortion of its crystals, almost as if a finger was rubbed along it while it was in the process of cooling:

Stone Five, June.

I found Stone Five on Gemstone Beach on 18 August 2025.

Stone Six (bottom row, right, in the Calendar), found on 23 March 2025, has the least number and most widely dispersed crystals of the six stones:

Stone Six, June.

Altogether, these six June stones illustrate how black stones with white spots are not all the same. Far from it, a great diversity exists. For even more specimens, see the 21 stones in Section 5 “Stones with Opaque White Crystals” in this Post in the Series “Gemstone Beach and its Stones: An Introduction for the Passing Motorist”.

A NOTE ON IDENTIFICATION ISSUES: Geological books and websites describe different volcanic and plutonic rocks but I find that working out which best fits a particular stone can be difficult. Take, for example, gabbro and diorite, both plutonic rocks. Their descriptions in the book “A Photographic Guide to Rocks and Minerals of New Zealand” (Mortimer, Campbell and Low, 2011) set out the differences as follows. It is noted there that gabbro and diorite can be very alike in the field but diorite is a little lighter in colour and has a speckled salt and pepper appearance. Gabbro consists of about 50% to 90% dark minerals, often augite or olivine, the rest being light-coloured plagioclase feldspar. Sometimes gabbro can have a greenish colour due to the presence of chlorite. Diorite consists of about 25% to 50% dark minerals (usually hornblende), the rest being plagioclase feldspar with minor amounts of quartz or orthoclase feldspar. The authors note that gabbro can be found between Colac Bay and Pahia in Southland, which is just a handful of kilometres east of Gemstone Beach. Diorite, they write, can usually be found in the same places as gabbro. So the six June stones could reasonably be gabbro or diorite. Photographic comparisons of gabbro and diorite on websites don’t always aid in distinguishing the two types of stones. When I consult University of Auckland Geology, gabbro looks distinctly darker than diorite, as expected (first two photos below) but other websites often cloud the issue, showing a variety of different types of rocks, even with different crystal shapes and sizes.

Gabbro. https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/gabbro.html
Diorite. https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/diorite.html
https://x.com/geologyshop/status/1364591037625339907
http://www.ftmmachinery.com/blog/what-is-gabbro-and-how-to-crush-it-for-construction-uses.html
https://earthknow.com/diorite-and-gabbro/

In regards to a specific stone found on a beach, it can be difficult to decide whether it might be gabbro or diorite (or even something else).

For July’s trace fossil stones, see this Post. These 2026 Calendars are for sale, with postage within New Zealand included, for $35 non-rural, $40 rural. Email me at john.tumblestone@gmail.com.

Four Polished Gemstone Beach Stones Gifted

The four polished Gemstone Beach stones I gave to our guests.
Stone One, Side A.
Stone Two, Side A – a mix of colours.
Stone Three, Side A.

Two recent overseas guests at our Air BnB in Whanganui showed a lot of interest in some of the stones I had collected and polished. A young couple, Omer and Elizabeth, booked in for one night and I greeted them and showed them where to go. I mentioned my hobby of tumble polishing beach stones and showed them a couple of colourful ones from a nearby garden (rejects from the tumbling process). This led to a walk over to my cluttered and untidy stone shed where I showed them my tumblers and some stones at various stages of processing.

The view from just inside the door of my stone shed.
Stones and tumblers.
The sink where a lot of the work with stones takes place.
The desk with my tumbling log, containers of grit and polish etc.
Ice cream cartons used to hold stones at different stages of processing.
Stones collected from beaches in the past.

Given their enthusiasm and appreciation, I decided to gift them four tumble polished stones from Gemstone Beach, three of which they had already seen and showed interest in, the fourth similar to some brecciated jasper that had also attacted their attention.

Gemstone Beach stones, March 2025.
Another March 2025 photo of Gemstone Beach stones.
Some stones collected from Gemstone Beach in March 2025.
The four polished Gemstone Beach stones I gave to our guests.

I had collected these four stones from Gemstone Beach, Southland, over the last couple of years. This beach is located 70 kilometres west of Invercargill, as described in this Post. I collect stones mainly from the beach in front of the carpark and further along to the Waimeamea River mouth – sections two and three in this Post.

Gemstone Beach, in front of the carpark.
The house in the cliff.
People often look for stones on Gemstone Beach.
More stone hunters, near the Taunoa Stream.
Seagulls near the mouth of the Waimeamea River.
Paragliders over Gemstone Beach.
Horse riders on Gemstone Beach.

A NOTE ON THE PHOTOS BELOW: Photos of stones often reveal a lot more than what can be seen when looking with the naked eye. There is much that is positive about this. Colours and patterns become more obvious, tiny details become visible. Close-up photos can show just how amazing an “ordinary” stone is. Stones One and Two below are good examples of this. There is also a negative side to the close-up photos of stones. They can reveal tiny scratches and imperfections in the polishing process, as well as less attractive aspects of a stone. Stone Three below has areas of white scratching which can lure your eye away from the amazing pink in it. Close-ups of Stone Four reveal how “dirty” some of its white crystals are. Generally, the positives well out-weigh the negatives – the photos allow you to explore a stone and appreciate it more more.

The first stone, Stone One, has really interesting circular features and patches of colour:

Side A of Stone One, amygdaloidal basalt??
Stone One, Side B.

Some of the circles could be amygdaloidal in character. Amygdaloidal stones are also known locally as volcanic bubble-infilled stones. They originate in molten magma which may contain dissolved gas that forms bubbles in the rock as the pressure is released on eruption. These bubbles can get trapped in the solidifying rock, forming tiny holes called “vesicles”. These holes then fill with mineral-rich fluids which leave behind deposits of minerals such as quartz, chalcedony, calcite and zeolites. The resultant “spots” are called “amygdales” (also “amygdules”). This term comes from the Latin and Greek words for almond, reflecting the almond-shape of many such in-filled vesicles. However, amygdales can also be round and some can be irregular shapes. Many of the dark-coloured stones with amygdales on Gemstone Beach are basalt, as Stone One could be. For other examples, see “A is for Amygdaloidal” and “Stone of the Day #17, Small Gemstone Beach Amygdaloidal Stone”. Further Gemstone Beach amygdaloidal stones can be seen in this Post, Section 4, Stones W30 to W42.

Stone One also has interesting white, orange, yellow and green in it:

Stone One, Side A.
Stone One, Side A.
Stone One, Side A.

These are various minerals that are present in the stone, and their distribution and intensity would most likely have occurred as the rock was cooling. They have made some fascinating patterns, some circular. Sometimes the colour is inside an amygdale, sometimes in the basalt itself. The white could be quartz, the green is probably epidote, and the orange and yellow could be orthoclase feldspar and/or iron oxide.

Stone Two is a colourful jasper. Elizabeth had mentioned she hadn’t seen a stone of this colour before. We also talked a little about the poppy jaspers in the 2026 TumbleStone calendar, the month of April, and Stone Two has some poppy-like orbs visible on Side B:

Stone Two, Side A.
Stone Two, Side B.

Jasper is an opaque form of cryptocrystalline, or microcrystalline, quartz which is also known as chalcedony. It is formed from microscopic crystals of silica, often precipitated out of heated groundwater flowing through sedimentary rocks (GeologyScience). It is the presence of iron oxide that provides the red colour. In Stone Two, Side A has a real mix of patches of light and dark reds, white, orange, purple and yellow. Side B has some large orb-like structures, with maybe the hint of tiny red orbs in the lower left quadrant:

Stone Two, Side A – a mix of colours.
Stone Two, Side B – the larger orbs.
Stone Two, Side B – a hint of tiny orbs??

Orbs in jaspers form because minerals crystallise in concentric layers around a nucleus or central point. If the orbs are red or orange, they look like a field of poppies from above.

Pink was another colour that Omaer and Elizabeth admired in my stones. Stone Three has some lines of intense bright pink in it:

Stone Three, Side A.
Stone Three, Side B.

Pink is often due to the presence of manganese. The rare pink stones found on Gemstone Beach are sometimes thulite, the national gemstone of Norway where it was first identified – see “P is for Pink”, also the month of March in the 2026 TumbleStone calendar. I’m not totally certain that Stone Three is thulite but the way the pink is presented in it is consistent with thulite. The non-pink material in the stone could be plagioclase feldspar (a guess) – if it was quartz, it would have polished in a much cleaner and more shiny manner. In my experience, thulite often fails to polish well.

Two further close-ups of the pink in Stone Three, and then two photos (below, right) showing how the pink stones stand out on the beach when wet (Gemstone Beach, 25 February 2021):

Stone Three, Side A.
Stone Three, Side B.
In the sand on the edge of a stream.

Stone Four is striking because of its elongated white crystals against a dark background (found in September 2024):

Stone Four, Side A.
Stone Four, Side B.

The crystals are likely to be plagioclase feldspar and my guess is that the stone could be either gabbro or diorite, both igneous plutonic rocks. The different sizes and shapes of crystals in such stones depends on how quickly the molten rock has cooled and hardened, and what minerals are present to make up the crystals. A “volcanic” rock cools on the earth’s surface and, because it has solidified quickly, the crystals have not had time to grow very large. But for a “plutonic” rock, the molten rock has cooled much more slowly underground, giving the crystals time to grow larger, sometimes as large as fingernails. Similar Gemstone Beach stones with opaque white crystals can be seen in this Post, Section 5, Stones W43 to W63. The month of June in the 2026 TumbleStone calendar has photos of six igneous stones with white crystals of varying shapes and sizes – the Post about them has not yet been completed. Here are four of June’s stones:

THE PROCESS OF TUMBLE POLISHING – The aim of tumble polishing is to mimic the action of the sea’s waves by turning stones over and over, letting them bump into each other. Adding sharp silicon carbide grit (like the abrasive stuff on sand paper) hastens the smoothing process. This takes place in a rubber barrel (or similar), about two-thirds full of stones, water and grit. The barrel is rotated 24 hours a day for a number of days. Usually three or four different grades (sizes) of grit are used. Tumbling stones in a very coarse grit for seven to ten days removes maybe five to eight per cent from the surface of the stones. Finer grits are then used, again for seven to tens days at a time. These remove less of the stone but makes the surface very smooth, ready for a final polishing stage in a very fine polish powder such as tin oxide. Sometimes a stage needs to be repeated until a stone is smooth enough.

4lb tumbler barrel.
In the tumbling shed.

I collect smooth beach stones so I need to do less tumbling than people who find stones in streams or the ground. Most of my stones take between about 50 to 60 days to polish. More details can be found in “2) The Seven Stages in Tumble Polishing Stones” in this Post.