January 2022 – TumbleStone

January 2022, Stone of the Day #31 – Gemstone Beach Black and White

The last stone in this Series comes from Gemstone Beach. It finished the polishing process on 22 December 2021. The white against the background of black made it stand out on the beach, along with the unusual shape of the light-coloured segments. The close-up photos reveal many interesting minor details, mostly crystals of both white and black.

A small thin stone, it is 3.5 cms long, 2 cms at its widest, and about 0.5 cms thick. Both of its largest sides are very smooth, except for one small crack, and there are a couple of small rough areas along the edge.

The other side of Stone #31.

Other black and white stones collected on Gemstone Beach in 2021, some of them amygdaloidal, some porphyry, some other kinds:

Amygdaloidal.

Porphyry.

Gemstone Beach, near the car park.

Gemstone Beach, looking south east.

Gemstone Beach, looking north west.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #30 – Gemstone Beach Greenie

Green stones can often be found on Gemstone Beach, from the pale green hydrogrossular garnets to the rich green quartzites to the light and dark greens of the argillites that contain trace fossils to green banded mudstones. This stone, found sometime in 2021, is a pistachio green in colour:

It is 4 cms by 3,5 cms, being about 1.5 cms thick. It has polished well and feels very smooth to the touch. The close-up photos have revealed some tiny rough areas.

Other side of Stone #30.

Examples of other stones found on Gemstone Beach demonstrating the range of greens to be found there:

https://tumblestoneblog.wordpress.com/2021/03/01/another-south-island-fossicking-trip-february-march-2021-days-9-and-10/

https://tumblestoneblog.wordpress.com/2019/05/06/nine-milestones-at-journeys-end/

https://tumblestoneblog.wordpress.com/2020/03/28/stay-at-home-day-three-28-march-2020-stone-three/

https://tumblestoneblog.wordpress.com/2019/06/27/16-gems-stones-for-poetry/

https://tumblestoneblog.wordpress.com/2021/06/30/g-is-for-green-hydrogrossular-garnet-and-h-is-for-hematite-jasper/

https://tumblestoneblog.wordpress.com/2021/07/22/i-is-for-ichnogenus-protovirgularia-and-j-is-for-jasper/

Found on Gemstone Beach in June 2020.

Found on Gemstone Beach in June 2020.

Some photos of Gemstone Beach taken during my last visit in September 2021:

Gemstone Beach car park.

Looking northwest along Gemstone Beach.

Near the Waimeamea River mouth.

Gemstone Beach near the car park.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #29 – Small Gemstone Beach Rhyolite Stone

It was only after visiting Slope Point a couple of times that I looked more carefully for rhyolite stones when visiting Gemstone Beach. The Slope Point rhyolites made me more aware of what kinds of stones would be rhyolite. And I started to find quite a few of them on Gemstone Beach. This one is quite a small stone but its wavy lines attracted my eye on the beach. It has a lot of similarities to Stone #27, though they were found some 140 kms apart:

The stone is 2.5 cms on its longest axis, 2 cms wide and 1 cm deep.

Other side of Stone #29.

Some of the “pattern” at the bottom of this photo are reflections, not part of the stone itself (see next photo).

Circled are reflections.

I tumbled the stone in 400 grit then 600 grit. After that, it was put in a 4lb barrel for tumbling in pro-polish tin oxide for 11 days, with a borax burnishing tumble for three days. The other 73 Gemstone Beach stones in the barrel included Stone of the Day #28. The photos below show that Stone #29 was one of the smaller ones in the batch.

The 74 polished Gemstone Beach stones in the 4lb barrel.

Stone #29 is one of the smaller ones.

Stone #29 is on the far right in the centre row.

Stone #29.

From a display in Orepuki.

Gemstone Beach, looking south-east. The people in the middle distance are standing in front of the car park.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #28 – Gemstone Beach “Melange”

In geology, a “melange” is a large-scale body of rock “characterized by a lack of internal continuity of contacts or strata and by the inclusion of fragments and blocks of all sizes, both exotic and native, embedded in a fragmental matrix of finer-grained material” (U.S. Geological Survey). However, in this Post, calling this stone a “melange” is simply drawing on the non-geological meaning f the word, a “varied mixture”. Stone #28 is made up of a melange, a mixture of crystals and/or fragments of various colours and sizes and shapes.

It was found on Gemstone Beach in 2021. After tumbling in 400 and 600 grit, it was polished using pro-polish tin oxide in a 4lb barrel for 11 days, followed by a three day borax burnishing tumble. The process was completed on 23 January 2022. There were 74 stones of various sizes in the barrel. Stone #28 has ended up very smooth and shiny over nearly all its surface, with only a couple of tiny rough areas on one of its edges.

The other side of Stone #28.

One of the edges of Stone #28.

Stone #28 is 5 cms long, 3 cms wide and 1.5 cms at its thickest. It was one of the larger stones in the 4lb barrel.

The 74 stones from the 4lb barrel in which Stone #28 was polished.

Stone #28.

Closer view of some of the stones from the 4lb barrel batch.

Stone #28.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #27 – Wavy-Line Slope Point Rhyolite Stone

This small stone, 3.5 cms long, is probably rhyolite. It comes from the same batch of Slope Point tumble stones as Stones #10, #12, #16 and #25. A dark stone, its rusty coloured wavy line caught my eye on the beach.

The other side of the stone also has some iron oxide staining.

Other side of Stone #27.

It has polished quite well, although there are three or four tiny holes remaining in its surface.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #26 – Grey Kakanui Stone with Shiny Inclusions

Some stones consist of a number of different substances, and not all of the substances may take a polish or polish to the same degree. Stone #26 is a good example of one such stone:

The grey material has not polished well but the small inclusions set within that grey material have:

Other side of Stone #26.

I don’t know what kind of material makes up this stone. On the beach, the bright inclusions against the grey background caught my eye.

Stone #26 is 4.5 cms long, 3 cms at its widest, and about 0.5 cm thick. It completed the polishing process three days ago. It was polished in a 3lb barrel along with another 56 stones from Kakanui. All the stones had undergone tumbling in 400 grit before spending 11 days in tin oxide tumble polish and three days in a borax burnishing tumble. The tin oxide mix had been used four times before (I usually re-use the mixes between six and eight times – six is the recommended number of times – I always record each time I use a mix and for how long). As can be seen in the photo below, Stone #26 stood out as the only stone that did not take a reasonably high polish.

The 57 stones in the batch, set out to dry.

Stone #26 (top, third from left) stands out as not taking a good polish.

The beach near Kakanui where Stone #26 was found.

Note: Jo from the North East of the UK posted a comment on a photo of this stone: “January 24th is my birthday and this year I went pebble hunting on our local beach… and found something very similar which I think is a Rhomb-Porphyry from Oslo.” According to Sandatlas, rhomb-porphyry is “a porphyritic igneous rock [andesitic] with abundant wedge- or lens-shaped anorthoclase (feldspar) phenocrysts. Rhomb-porphyry is a rare rock type. The most well-known is the rhomb-porphyry from the Oslo Rift in Norway. Similar rocks are known to exist in only two other locations: The East African Rift Valley and the Antarctic.” Stone #26 certainly looks similar to photos of rhomb-porphyry (a “rhomb” is like a “pushed-over square”, where all sides are of the same length, though the phenocrysts in examples tend to be of a variety of shapes):

Source: www.sandatlas.org/rhomb-porphyry/

Source: http://www.sandatlas.org/rhomb-porphyry/

Rhomb shape. Source: www.iconexperience.com/o_collection/icons/?icon=shape_rhomb

Rhomb shape. Source: http://www.iconexperience.com/o_collection/icons/?icon=shape_rhomb

Source: http://www.sandatlas.org/rhomb-porphyry/

Whether Stone #26 is a “rhomb-porphyry” or not would require a geochemical analysis. Jo has made a very interesting suggestion which has led me to find out more about the great diversity of stones on the planet.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #25 – Slope Point Volcanic Breccia?

In this stone, found on a Slope Point beach in 2021, many small fragments are packed tightly together. [Though see the Note at the end on this Post about whether it is breccia or not.]

Stone #25 was tumbled in 400 grit then in 600 grit. After 13 days in tin oxide tumble polish, it had a three day borax burnishing period, being in the same 3lb barrel as Stone #10, Stone #12 and Stone #16. There are some remaining tiny areas that are not completely smooth but I proceeded with the polish as I did not want to reduce the stone further. It ended up being 4 cms long, 2 cms at its widest, and 1 cm thick.

Other side of Stone #25.

[NOTE, 25 January: My limited knowledge of geology led me to think this could be breccia. However, the “fragments” are unusual and I had at the back of my mind the thought that they could be crystals of some kind. After I posted the Post, Mathew Vanner kindly made the following comment on the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils“: “I am not sure that this rock is brecciated – I think it is an igneous with large maybe feldspars in a fine groundmass.” Mathew has a background in geology and the Southland region (see the Post on Stone #17) and his suggestion is probably more reliable than my original thinking.]

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #24 – Trace Fossil Stone from Gemstone Beach

This stone is a light coloured argillite with trace fossil markings on it. It is another stone from the 22 December 2021 batch that Stones #19, #20 and #23 came from. Trace fossil markings can sometimes be difficult to see in photos so I have provided darker and lighter versions of some of the close-ups:

Close-up A.

Darker version of Close-up A.

Lighter version of Close-up A.

Close-up B.

Darker version of Close-up B.

Lighter version of Close-up B.

These traces were likely left in ocean floor sediment about 250 million years ago, probably by a small burrowing animal, some kind of worm or shellfish. Some of the traces look like they may have started as ripples in the surface sediment left by a fish swimming close by. Sometimes the traces can be seen on only one side of the stone, and if appearing on both sides (if the stone is relatively thin and flat) they can be quite different.

Other side of Stone #24.

Argillite tends not to take a high polish and, in order to preserve the traces, I tend to start with only a 400 grit tumble before polishing.

For more information on TumbleStone Blog about these trace fossils, see Photo-Book “The Trace Fossil Stones of Gemstone Beach”; the Series of Posts that begin with The Fossilised Worm Cast Stones of Gemstone Beach and Riverton – Part One: Initial Identification; “I” is for “Ichnogenus Protovirgularia”; and “U” is for “Unusual Variations of Trace Fossil Stones” and “V” is for “The Chevron Shape of Trace Fossils”.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #23 – Highly Polished Complexity from Gemstone Beach

There were 60 stones in the 3lb barrel of Gemstone Beach stones that completed the polishing process on 22 December 2021. Stone #19 and Stone #20 were in that barrel, along with today’s stone, Stone #23.

The 60 stones from Gemstone Beach polished on 22 December 2021.

Stone #23.

Stone #20, a brown hydrogrossular garnet.

Stone #23 is maybe the most highly polished stone in this batch, which means it is difficult to photograph without reflections interfering more than usual:

The stone is astonishingly complex. It looks like it might be at least partly brecciated, with many small fragments within it, but the surface has polished very smoothly and seems to have taken a depth of polish.

After a tumble of about 10 days in 400 grit, this stone was tumbled for a similar period in 600 grit before spending 17 days in tin oxide tumble polish and 9 days in a burnishing borax tumble.

The other side of Stone #23.

The stone is 3.5 cms long, 3 cms wide and 0.5 cm thick. I am not sure what kind of stone it is.

The Index to the January 2022 Stone of the Day Series is here.

January 2022, Stone of the Day #22 – A Timaru Quartzite with Windows

My first batch of polished stones from Timaru was completed on 19 January 2022. The beach that they came from is described in the Post on Stone #21, except that I accessed it at the end of Ellis Road, a little south of Scarborough Road. The actual day I found Stone #22 was Sunday 27 June 2021, on a foggy morning, and two photos of it appear in a Post on that visit. This is the polished stone, with a small number of blemishes apparent:

It is a stone with two different coloured faces, one red and the other yellow:

The other side of Stone #22, the yellow side.

One of the most interesting aspects of this stone is the “windows” into it, small clear inclusions. There are hundreds of them, many very tiny. These I have elsewhere called “entrances”. Sometimes, though not often, these can come loose in the tumbling process, and one end of Stone #22 has a hole in it from a missing window.

One end of Stone #22 has a missing “window”.

Small hole in the end of Stone #22 (on left).

Lots of “windows”, some very tiny.

Comparing the polished stone with the stone the day it was found on the beach gives an idea of the extent to which the “windows” have been reduced during the tumbling:

Stone #22 when found on beach.

Stone #22 after tumble polishing.

Stone #22 when found on beach.

Stone #22 after tumble polishing.

Stone #22 is 4.5 cms long, 2.5 cms wide and around 1 cm thick. It was put in a 400 grit tumble for 10 days followed by another 10 days in a 600 grit tumble. After 11 days in tin oxide tumble polish, it underwent a borax burnishing tumble for three days.

The carpark at the end of Ellis Road, south of Timaru.

Stones on the beach, Timaru.

The stretch of beach where I found Stone #22.

The Index to the January 2022 Stone of the Day Series is here.