Category: Kai Iwi Beach

Fifty Polished Kai Iwi Beach Stones for the Book Man: Part Two, Stones 11 to 20

I gifted 50 polished stones found on Kai Iwi Beach, near Whanganui, to Cam who sold me some books at a good price. Many of the stones I gave to Cam are some variety of quartz, the predominant type of stone on Kai Iwi Beach. Part One describes the background and the first ten stones.  This Post describes another ten of these stones.

Stone 11  again consists primarily of quartz, with only a light sprinking of iron oxide in it. You can’t see many quartz crystals in it due to their tiny size and tight compaction:

Stone 11.
Other side of Stone 11.

By contrast, Stone 12, another quartz, has hardly any iron oxide in it and some small clear quartz crystals are much more obvious in it:

Stone 12.
Other side of Stone 12.

In Stone 13, the iron oxide is laid down across only part of the stone so that where it is absent appears as white bands of varying width:    

Stone 13.
Other side of Stone 13.

Stone 14 is what I call a “two-sider” – the two sides differ enough from each other that you could be forgiven for thinking they might belong to two different stones. The main difference is the absence or presence of yellow:   

Stone 14.
Other side of Stone 14.

I am not sure what type of stone is Stone 15. It’s not the usual iron oxide-stained quartz. It contains a mineral that gives it a green hue, and the rectangular-like crystals in it are probably not quartz but are more likely plagioclase feldspar, another very common rock-forming mineral:

Stone 15.
Other side of Stone 15.

Stone 16 is a small dark red jasper. Jasper is a type of chalcedony or microcrystalline quartz, a dense aggregate of microscopic quartz crystals too small to be seen with the naked eye. It is opaque due to the presence of minerals which give it colour, with the red of iron oxide being most common. Jasper is usually classified as sedimentary, precipitating from solutions moving through the ground.   

Stone 16, jasper.
Other side of Stone 16.

The stone could be called a “brecciated” jasper, having been fragmented to some extent by tectonic stress. The small areas between the fragments have become veins as they have been filled by mineral. The larger veins contain some white quartz, stained yellow/orange. The many fine veins in the stone have been filled with a clear mineral which could, again, be quartz. “Brecciation” has previously been explained in relation to Stone 2 (see Part One).

Stone 17 is a white quartz – you can see tiny clear crystals in the close-up photos which are embedded in a “frothy” white quartz mix, likely to contain water and/or air: 

Stone 17, quartz.
Other side of Stone 17.

It is similar to Stone 12 (above, earlier in this Post) but the shape and distribution of the tiny clear crystals is a bit different.   

Stone 18 has some similarities to Stones 4 and 9 (see Part One), consisting of white, yellow, brown and black crystals:

Stone 18.
Other side of Stone 18.

The white is quartz, the yellow and brown is iron oxide, and the black (sometimes sparkly) will be mica.

 Stone 19 has an unusual black patterning on it, one that caught my eye on the beach:    

Stone 19.
Other side of Stone 19.

Again the stone is quartz with some yellow/orange iron oxide, but I am unsure what the black mineral is.

Stone 20 is completely black:

Stone 20.
Other side of Stone 20.

There are a few tiny light areas on each side of the stone, hinting that it is quartz that has been flooded by a black mineral. I used photo software (Picasa 3) to lighten the close-up images to reveal some of the subtle patterns on the stone’s surface – on the left are the original images, on the right are the lightened ones:

Part Three, Stones 21 to 30, is not yet available.  

Fifty Polished Kai Iwi Beach Stones for the Book Man: Part One, Stones 1 to 10

Recently I was wanting to buy some books on Scottish Island knitting patterns on behalf of my wife. I inquired at my favourite local secondhand bookshop, Book Hunters on Ridgway Street in Whanganui. There I spoke to Cam who said they had none in stock but he would look out for them, and he wrote my contact details in his book. Not long afterwards, he rang to say he had found a bunch. They were just what I was after, and he gave me a good deal on them. I knew he lived at Kai Iwi Beach so I asked whether he would be interested in a gift of some tumble polished stones from there. He said yes, so I have picked out 50 to give to him. 

Kai Iwi Beach is my local beach and from time to time I walk Jasper the dog there. There are not many stones on that beach – in fact, the area is much better known for fossils, especially of moa. The nearby village is called Mowhanau and it is thought the name could have originally derived from “moa-whanau”. I automatically look for stones when I am on any beach. As a result, over the past few years I have collected quite a few from Kai Iwi Beach that I have gone on to tumble polish. Most of them are quartz that have been stained yellow-orange by iron oxide – see “The Iron-Stained Stones of Kai Iwi Beach”. A few other stone types occur, and I recently found a trace fossil in argillite and an orbicular jasper, both rare. With even ordinary appearing stones, however, when they are viewed up close, there is quite a variety of interesting colours and patterns in them.   

Jasper on Kai Iwi Beach.
Second hand books from Book Hunters.
Fifty polished Kai Iwi Beach stones.
Some of the stones.

 The 50 stones given to Cam are presented in this series of Posts in no particular order. The first ten are below.

 Stone 1 could be mistaken for a jasper, given its red hues. However, it is more likely to be quartz with its colour due to the presence of iron oxide:     

Stone 1, a type of iron oxide-stained quartz?
Other side of Stone 1.

Quartz is one of the most common minerals on Earth and is hard and glassy. Its purest form is rock crystal which is colourless and transparent. However, more often quartz stones incorporate other minerals which give them colour and make them opaque. Iron oxides include a number of chemical compounds such as hematite and limonite. They can colour stones a number of hues, from yellow to orange to red to brown and even black.

Stone 2 could be a mudstone because of its very fine grained and smooth character. Mudstone is a sedimentary rock, often laid down on the ocean bed. But what is most interesting about Stone 2 is that it has fragmented in places due to tectonic stress. Great weight of rock can move slightly and deform or break-up what lies beneath. The fragments in Stone 2 are angular which means the stone could be viewed as a kind of breccia – see “T is for a Type of Tiny Tectonic Breccia?”   

Stone 2, brecciated mudstone?
Other side of Stone 2.

Stone 3 is more typical than Stone 1 for the kind of iron oxide-stained quartz from Kai Iwi Beach, being more orange-yellow in colour. It is more spherical in shape than most of the stones on the beach which tend to have two distinct flat sides:    

Stone 3, typical Kai Iwi Beach iron-stained quartz.
Other side of Stone 3.

Stone 4 is made up of lots of tiny bits of quartz and other minerals. It could be a kind of sandstone, formed from the compaction of these tiny bits, though most sandstones have finer grains:     

Stone 4.
Other side of Stone 4.

Stone 5 is another iron oxide-stained quartz but the mineral is distributed within the stone quite differently from Stone 3, with the quartz itself sometimes showing white around the edges: 

Stone 5.
Other side of Stone 5.

Stone 6 appears in some ways to be a more compact version of Stone 4, made up of lots of tiny bits of quartz with iron oxide providing a yellow-orange colour: 

Stone 6.
Other side of Stone 6.

Stone 7 is again likely to be made up primarily of quartz but there is a black mineral in it providing a different character to the previous stones:

Stone 7.
Other side of Stone 7.

Some stones look different on different sides. Stone 8 is an example of this. Again, it is an iron oxide-stained quartz, similar in many ways to Stone 5, but the distribution and pattern of the colour-providing mineral varies a lot on the two different sides:    

Stone 8.
Other side of Stone 8.

Stone 9 has some similarities to Stone 4 but has more small dark mineral bits in amongst the tiny quartz crystals. I suspect some of the dark bits are biotite mica, which also sparkle when they catch the light just right:    

Stone 10, the final one in this Post, is again an iron oxide-stained quartz. Some areas of the stone have no colour-providing mineral in it and it seems as though you can see into the quartz to some extent:  

Stone 10.
Other side of Stone 10.

Stones 11 to 20 are described in Part Two.  

Tumbling an Orbicular Jasper Found on Kai Iwi Beach, Whanganui

Currently I am spending most of my time working on a photo book on Gemstone Beach stones. At this stage, I have collected together photos from the last four years and drafted text for entries on 20 diffferent stone types. I am just finishing writing six sections for the Introduction. I next need to edit some of the text I write earlier, to improve it. Chrissy is working on the layout, and we will eventually need to get together to finalise things.

But I am also finding the opportunity to tumble some stones, including this Kai Iwi Beach one. I found it about ten weeks ago and think it is probably an orbicular jasper – see this Post. I have recently tumbled it in 400 grit for 11 days and then in 600 grit for 10 days. It has come out nice and smooth, ready to go to a final polish stage. When found, the orbs in the stone were raised, suggesting they are harder than the rest of the material. I wasn’t sure if tumbling might not produce a completely smooth surface, but it has. Following are photos of the stone as found (below, left) followed by the stone after tumbling to date (on the right):

Stone when found.
Stone after 400 and 600 grit tumble.
Stone when found.
Stone after 400 and 600 grit tumble.
Stone when found.
Stone after 400 and 600 grit tumble.

The orbs have an interesting structure and are nicely defined. I am pleased with progress so far and look forward to seeing what it looks like when polished. 

Orbicular Jasper Find? Kai Iwi Beach, Whanganui

A week ago, near the end of February, I was taking the dog for a walk on Kai Iwi Beach, just north of Archer’s Bridge which crosses the Kai Iwi Stream. I usually keep an eye open for interesting stones – most of the widely-scattered stones along this beach are iron-stained quartz, with the occasional rare green argillite with a trace fossil. I spotted this small stone in the dry sand and it looked different from the usual ones. The surface of the stone that was showing didn’t have the dullness I’m most used to seeing here. There seemed to be a bit of a sheen to it. So I picked it up to check it out. Turning it over, I was very surprised to see what looked like lots of tiny orbs on part of the stone. And the orbs seemed to stand out from the rest of the stone a little, as if they were harder:

One side of the partly-orbicular stone.

The other side of the stone:

As I have noted in this Post, orbs form due to the presence of minerals which crystallise in concentric layers around a nucleus or central point, giving rise to orb-like structures. Many of the “orbs” in my Kai Iwi Beach find appear to have some kind of structure, with a central point apparent in some. And the stone itself could be jasper, given its fine-grained character and colour – I have had similar coloured stones from the Coromandel identified for me as jasper. I am not aware of such a find before on this beach (or nearby).

This Post examines the stone after some tumbling.

S is for Scoria

This is an expanded version of my letter “S” 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 “S is for Slope Point Stone”. 

S is for Scoria

Large red scoria stone (wet), Kai Iwi Beach.

On my current morning walks on Kai Iwi Beach (near Whanganui) with dog Jasper, I am getting a more detailed understanding of the range of stones to be found here. They are quite widely scattered but that makes it easier to spot interesting ones. For more on this beach and its stones, see “The Iron-Stained Stones of Kai-Iwi Beach” and “K is for Kai Iwi Beach Stone”.

About three weeks ago I became intrigued with a type of stone I had previously just ignored, and I think it’s scoria. It’s like pumice but harder, more dense, and feels rougher. Most of these stones are dark red, some are grey, and they often have small black and white crystals in them. Despite their roughness and many tiny holes, I decided to collect a few and tumble polish them, just to see the results. Some are now undergoing a 220 grit tumble (see NOTE ON TUMBLING below).

I’ve found a range of colours of scoria on Kai Iwi Beach.
A light brown specimen, showing various “bits” in it.
Early morning, on the way down to Kai Iwi Beach with Jasper.
This is where I find the scoria, among the scattering of stones on Kai Iwi Beach.
Kai Iwi Beach, awaiting some rain.
Jasper on Kai Iwi Beach, patiently waiting while I pick up stones.

As Wikipedia informs me, scoria is a pyroclastic, highly vesicular, dark-coloured volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air. It is typically dark in colour (brown, black or purplish-red), and often basaltic in composition. Scoria has a relatively low density as it is riddled with vesicles (tiny hollows from gas bubbles), but in contrast to pumice, scoria always has a specific gravity greater than one and sinks in water.

Coincidentally, my wife bought some scoria recently for the greenhouse floor – it’s brighter and more chunky than the water-smoothed specimens I find on Kai Iwi Beach. Commercial scoria often comes from the Auckland volcanic field which includes hills of this type of rock, and it is sometimes excavated for building materials and landscaping. See Geotrip to “Big King Scoria Cone”.

Commercial scoria in the greenhouse – to the right are some of my swan plants waiting to grow a bit more before being put outside for the monarch butterfies.
Commercial scoria. Rougher and chunky.

Another coincidence: I live on Rapanui Road, and on Rapa Nui/Easter Island, reddish scoria was used to carve the pukao (topknots) for the famous moai statues, and even for the main bodies of some moai – see “Constructing the Rapa Nui moai”.

Scoria top knots on Rapa Nui moai. http://www.researchgate.net/publication/320236368_Using_Structure_from_Motion_Mapping_to_Record_and_Analyze_Details_of_the_Colossal_Hats_Pukao_of_Monumental_Statues_on_Rapa_Nui_Easter_Island/figures?lo=1
Rapa Nui/Easter Island moai with red scoria pukao on its head https://en.wikipedia.org/wiki/Scoria. This is a close up of the moai at Ahu Tahai, restored with coral eyes by the American archaeologist William Mullo.

An interesting comment on my Post in the Facebook Group was made by Bruce Taylor, a local fossil hunter: “Some of the stones found here used to be moa, as in they are from fossilised bones. Rare and hard to spot. Exceptional shark teeth also with fossilised root that is now stone. Wood, seal, dolphin, penguin, all rare but found and in stone. Examples can be seen at the camp ground.”

NOTE ON TUMBLING: I tumbled some scoria stones for a few days in 220 silicon carbide grit. The resultant slurry contained a lot of fine fragments that had come off the stones. Many of the tumbled stones felt relatively smooth, certainly a lot smoother than beforehand. Five of the more interesting ones:

Four more:

However, close inspection showed that, as could have been anticipated, there were still a lot of tiny holes and further tumbling would not have resulted in a smooth polished product. Tiny bits of scoria loosened throughout the process would also contaminate later barrels and loads, an issue identified by John Taylor (Scotland) in a comment on my Facebook Group post. I have therefore decided not to proceed any further with them.

The next Post in this Series is “T is for a Type of Tiny Tectonic Breccia?“. An Index for this Alphabetical Series is here.

Finally Found! A Small Trace Fossil Stone from Kai Iwi Beach

Trace fossil stone.
Trace fossils in dark green argillite. They have eroded at a slower rate than the host argillite.
Stress fractured trace fossil.
Nice dark trace fossil.

One of my favourite types of stones to find at Gemstone Beach in Southland is the argillite that has trace fossils in it (see photos above). There are a few variations of them, with different coloured stones (green, red, black…) and different trace shapes (the most attractive to me being the lines of chevrons). There are lots of these stones there, and I have found them too at Riverton Aparima. See, for example, “Southern Sojourn 2023(18): The Tattooed Rock, The Trace Fossils… Revisiting Gemstone Beach’s Trace Fossil Stones, February 2023” and “U is for Unusual Variations of Trace Fossil Stones and V is for The Chevron Shape of Trace Fossils”.

I have become aware that trace fossils in argillite can also be found elsewhere in New Zealand. After I moved to Whanganui a few years ago, I was told that on rare occasions they could be found on nearby Castlecliff Beach, then my wife found a couple on South Beach when riding her horse there. Bruce Taylor, a keen fossil hunter, showed me a couple he had found on Kai Iwi Beach. These have all been green stones, the most common colour down south too. I have been keen to find one for myself. For a few weeks, I have been walking our dog early in the mornings on Kai Iwi Beach:

Jasper the dog waiting for me on the walk down to the beach. Down below is Archer’s Bridge across Kai Iwi Stream.
On the beach.
On a large lump of fallen mud. from the cliff.
A great beach for a dog to get some exercise.

During our walks, I constantly scan for stones to tumble polish. There are very few stones there, usually widely-scattered, and not many are colourful or interesting. Mainly iron-stained quartz can be found, which often tumble polish well – see “The Iron-Stained Stones of Kai-Iwi Beach” and “K is for Kai Iwi Beach Stone” . I always hope to come across an argillite with trace fossils but for a number of years, my hunt has been fruitless, without even a green argillite being spotted. Then last week I finally found a small green argillite with a trace fossil!

Small green argillite with trace fossil, Kai Iwi Beach.
Other side of stone.

It’s quite small and innocuous. The main trace fossils in it, probably burrows, are rather plain. There are hints of maybe other smaller traces, difficult to see. But to me, this is an outstanding find, long awaited.

The waves have rearranged quite a bit of sand on Kai Iwi Beach recently, mostly removing it along one particular stretch of a couple of hundred metres. As a result, there seems to have been an increase in the scattering of stones that appears along the wave’s edge. That’s where I found this small trace fossil stone, more than 500 metres north of Archer’s Bridge, the pedestrian bridge over the Kai Iwi Stream.

More stones scattered along the beach than usual.
This large log used to sit on sand.
I witnessed this large slip recently – photo taken just after it happened.

Whenever I am on any beach, I can’t help but scan for stones. For the next few weeks, I will be on Kai Iwi Beach each morning, walking the dog so, who knows, another one might turn up. Or not.

K is for Kai Iwi Beach Stone

This is my eleventh contribution to the current Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I also posted “K is for Kai Iwi Beach Stone”, though it was a different stone.

K is for Kai Iwi Beach Stone

Iron stained quartz.
Jasper the dog on Kai Iwi Beach.
Jasper looking up at the pigeons sitting on the stack.
Kai Iwi Beach as sun sets.

I sometimes take Jasper the dog for a walk on nearby Kai Iwi Beach, about 12 kilometres north of Whanganui. The beach is much better known for fossils than stones, the fossils coming from the crumbling cliffs. In fact, there aren’t many stones there, mainly a light scattering on patches of the beach. But somehow whenever I’m on a beach, my eyes look for stones that can fit into a tumbling barrel. I usually come away with up to a dozen. The vast majority of them seem to be iron stained quartz, like this one, which I recently tumble polished. See “The Iron-Stained Stones of Kai-Iwi Beach”. The dog loves the beach – it provides him with lots of things to explore and plenty of running opportunities, as well as a chance to meet up and play briefly with other dogs. Photos of the beach above were taken on my phone.

The next Post in this Series is “L is for Leithfield Beach ‘Looker’”. An Index for this Alphabetical Series is here.

Recently Polished Stones: Three Outstanding Specimens

These three stones were collected on different beaches – Orepuki’s Gemstone Beach in Southland, Kakanui’s Seadown Beach in North Otago, and Kai Iwi Beach near Whanganui.

The first stone was found by me on Gemstone Beach on Wednesday 6 March 2024 (see this Post). I stated at the time: Some of my finds today were spectacular, this one in particular. I found it down near the Waimeamea River lagoon. The colour is unique amongst the stones I have found on this beach so far. I suspect it is a jasper, partly because it contains hematite. It is very smooth, almost perfectly so. It was very smooth and its spectacular character was obvious. It is 4.5 cms long. Tumble polishing has succeeded in clarifying those things. Side A (below) includes a cream-coloured vein, part of which is transparent, penetrating part way into the stone.

Side A.
Side A.
Close-up of top left of Side A.
Close-up of bottom right of Side A.

On Side B, the same cream-coloured vein is again apparent:

Side B.
Side B.
Top centre of Side B.
Bottom centre of Side B.

Some comparison photos of the stone when found and when polished, illustrating how I often collect beach stones whose colour and patterning are already clear and intriguing, though they have to be wet to see them at their best:

The polishing process results in a stone that is always clear – it doesn’t have to be wet to show its true colours.

The second stone is a larger one, from Kakanui’s Seadown Beach. It has been in my stone stores for a number of years, mainly because of its size (7 cms long). I needed to tumble it in a large barrel, 6lb or 12lb, and I had set it aside for that and didn’t rediscover it until recently. It is a quartzite, a fairly common type on stone on this beach, and it can also be found along the coast right up to Canterbury, including Birdlings Flat. Their size varies quite a bit, as does their colour. Yellow is the most common colour though grey and red also occur. See the Wednesday 26 May 2021 entry in this Post for more information on these quartzites. Quartzite stones tend to tumble polish very well. This one has a handful of tiny holes remaining, but I didn’t want to reduce its size to remove them. The stone more patterning than often the case with quartzites, with some red on Side A…

Side A.
Side A.
Side A’s red patch.
Lower left section of Side A.

…and two large circular orange features on Side B.

Side B.
Side B.
Top centre of Side B.
Bottom centre of Side B.

The third stone was picked up on Kai Iwi Beach, probably while I was walking our dog Jasper. It is the smallest of the three stones, at 4 cms long. While Kai Iwi Beach does not have the gems of Gemstone and Seadown Beaches, I find it hard ignore anything shiny and patterned there. Most of the stones I collect on Kai Iwi Beach are iron stained quartz, but there is a diversity of patterns in such stones. I picked up this stone because of the white patches, one of them looking a bit like the continent of South America.

Side A.
Side A.
Bottom right of Side A.
Centre of Side A.

Side B shows the same kind of white patches – close-ups of the patches reveal the sugar-like grains of quartz:

Side B.
Side B.
Top right of Side B.
Bottom left of Side B.

In between my stones collecting trips to the South Island (the next one is planned for September, two months away), I continue to tumble polish stones.