May 2020 – TumbleStone

Alert Level Two, Saturday 30 May – Stone 8, Green Breccia-like Stone from Riverton

Stone 7 of Level Two.

Stone 6 of Level Two.

Stone 5 of Level Two.

Stone 4 of Level Two.

Stone 3 of Level Two.

I have seen a few stones like these on the beaches of the south coast, all of them green. They fascinate me as they seem to be put together from small bits and pieces, all variations on green. Is it a breccia, a stone made up of randomly oriented angular fragments cemented together in a fine-grained matrix, the fragments not previously eroded by water or wind? I don’t know, the fragments are very small.

Stone 8 of Level Two, from Riverton.

One side of Stone 8 of Level Two.

Stone 8 of Level Two.

The close-up images show you more of the stone’s constituent pieces:

Close-up of Stone 8 of Level Two.

Stone 8 of Level Two.

Close-up of Stone 8 of Level Two.

It is hard to get a completely smooth polish from such a stone. Not all the segments are of the same hardness and so some may not polish at all. Others are brittle. Sometimes a small piece can come loose in the tumbling process.

View of the edge of Stone 8 of Level Two.

Stone 8 of Level Two.

View of a different part of the edge of Stone 8 of Level Two.

Alert Level Two, Wednesday 27 May – Stone 7, Black Veined Stone from Gemstone Beach

Stone 6 of Level Two.

Stone 5 of Level Two.

Stone 4 of Level Two.

Stone 3 of Level Two.

Stone 2 of Level Two.

Stone 7 of Level Two is large enough to need to be tumbled in my biggest barrel, the 12lb one. I picked it up from Gemstone Beach because of the pattern of dark veins apparent on one side.

Stone 7 of Level Two.

The plainer side of Stone 7 of Level Two

Stone 7 of Level Two.

It could be a veined argillite, but I am unsure. The green-grey of the stone is very similar to the more common argillites in which fossil worm casts can be found:

Close-up of Stone 7 of Level Two.

What made me stop on the beach and pick it up was the distinctive black veins on one side of this stone:

Close-up of veins in Stone 7 of Level Two.

Stone 7 of Level Two.

Close-up of a vein in Stone 7 of Level Two.

Close-up of veins in Stone 7 of Level Two.

There are a number of small cracks and tiny rough patches in the stone, with a small chunk out of the bottom. Removing these by further tumbling with silicon carbide grit would have resulted in unpredictable changes to the surface pattern of the veins, and a smaller stone, undermining its visual impact.

Small chunk out of the bottom of Stone 7 of Level Two.

Alert Level Two, Monday 25 May – Stone 6, Quartzite-Like Stone from Birdlings Flat

Stone 1 of Level Two.

Stone 2 of Level Two.

Stone 3 of Level Two.

Stone 4 of Level Two.

Stone 5 of Level Two.

This stone was polished last month, having been found on Birdlings Flat over a year ago:

Stone 6 of Level Two.

Other side of Stone 6 of Level Two.

Stone 6 of Level Two.

I initially thought it was a quartzite. The Stone of the Day Series in Level Four included six quartzites: Stone Two, Stone Nine, Stone Twenty, Stone Twenty-Seven, Stone Twenty-Nine and Stone Thirty.

Stone 2 of Level Four.

Stone 9 of Level Four.

Stone 20 of Level Four.

Stone 27 of Level Four.

Stone 29 of Level Four.

Stone 30 of Level Four.

As I mentioned in a previous Post, A quartzite starts off as a quartz-rich sandstone, a sedimentary rock that is grainy and feels like sandpaper. When the sandstone is exposed to high temperatures and pressures, the hard glassy metamorphic rock of quartzite is formed. Quartzite’s wide variety of colours are a result of minor amounts of impurities being incorporated with the quartz during the process of metamorphism.

However, the close-up images of Stone 6 of Level Two do not reveal the grains I would expect of a metamorphic quartzite but rather a set of crystalline structures closer to quartz itself.

Close-up of Stone 6 of Level Two.

It is only when looking at such images that the complexity of the stone can be appreciated – the various veins running through it, different inclusions, small iron stains, darker and lighter patches:

Close-up of Stone 6 of Level Two.

Stone 6 of Level Two.

Close-up of Stone 6 of Level Two.

Alert Level Two, Saturday 23 May – Stone 5, Fossil Worm Cast Stone from Gemstone Beach

Stone 1 of Level Two.

Stone 2 of Level Two.

Stone 3 of Level Two.

Stone 4 of Level Two.

This is a small green-grey argillite stone with a number of small fossil worm casts and some dark veins. I have found such stones on beaches at Riverton and near Orepuki. This one comes from Gemstone Beach.

Stone 5 of Level Two.

One side of Stone 5 of Level Two.

Stone 5 of Level Two.

Close-ups reveal more details about the dark veins and the worm cast trace fossils:

Close up of a white intrusion in Stone 5 of Level Two.

Stone 5 of Level Two.

Close up of Stone 5 of Level Two.

Close up of trace fossil and dark veins in Stone 5 of Level Two.

Close up of some of the dark veins in Stone 5 of Level Two.

The process of producing the images and the close-ups, using three stages of cropping along with saturation, “lightening”, and some “shadowing” (to darken the veins):

Original image.

Original image cropped.

Cropped image “saturated” and “brightened”

Stone 5 of Level Two.

Original image.

Original image cropped.

Further cropping of cropped image.

Cropped image after saturation and adjustments using lightening, darkening and brighting.

Alert Level Two, Wednesday 20 May – Stone 4, Polished Cloudy-Green Stone from Riverton

Stone 1 of Level Two.

Stone 2 of Level Two.

Stone 3 of Level Two.

I found this stone on the Back Beach, Riverton, but I am unable to identify it. It has a couple of small patches of white quartz in it, and the close-up views suggest it may be a kind of stained quartz. One of its significant features is the cloud of green found mainly on one side. It has polished well, with just one small rough area close to the largest white quartz patch.

Stone 4 of Level Two.

One side of Stone 4 of Level Two.

Stone 4 of Level Two.

Top view of Stone 4 of Level Two, showing white quartz patch and rough area.

Bottom view of Stone 4 of Level Two.

Stone 4 of Level Two.

Top view of Stone 4 of Level Two, showing white quartz patch.

Close-ups of the stone reveal characteristics of its quartz make-up and its green staining:

Stone 4 of Level Two.

Close-up of Stone 4 of Level Two.

Close-up of Stone 4 of Level Two.

Alert Level Two, Monday 18 May – Stone 3, Banded Argillite from Gemstone Beach

Most grey banded argillite stones found at Riverton and Gemstone Beach are similar to Stone of the Day Twenty-Four – the bands are well defined, with a straight boundary between them. Stone 3 of Alert Level Two is different – the lines between bands are wavy, almost like a water colour painting where one colour “bleeds” into another.

Stone 3 of Level Two.

Other side of Stone 3 of Level Two.

Stone 3 of Level Two.

The cropped close-up images show that lots of tiny specks of different colours are embedded in the stone. The last image below also shows the start of two tiny cracks that run across the stop of the stone.

Stone 3 of Level Two.

Close up of Stone 3 of Level Two.

Close up of dark area and start of tiny cracks of Stone 3 of Level Two.

The original and posted images of each side of the stone, showing the minor changes made for this Blog:

Original image of one side of Stone 3 of Level Two.

Stone 3 of Level Two.

Original image of other side of Stone 3 of Level Two.

Other side of Stone 3 of Level Two.

Alert Level Two, Saturday 16 May – Stone 2, “Marble-Type” from Riverton

This stone comes from the Back Beach, Riverton. It is what I call a “South Coast marble type” stone. These come in predominantly white or yellow, with black or rust-coloured veins. As noted in the Post on Stone of the Day Eighteen, this type of stone can be difficult to polish and often has patches of roughness or tiny holes that can be difficult to remove.

Stone 2 of Level Two, a polished “marble-type” stone, comes from the Back Beach, Riverton.

Stone 2 of Level Two.

Stone 2 of Level Two has polished with very few “imperfections”. And its patterns are intriguing:

Stone 2 of Level Two.

Detail of Stone 2 of Level Two.

This vein contains some holes. Detail of Stone 2 of Level Two.

Detail of Stone 2 of Level Two.

The stone has a deeper colour than most “South Coast marble type” pebbles. This meant that the preparation of the images for this Post included the challenge of “lightening” it whereas most stone images require a “deepening” of hue.

Original image of first side of Stone 2 of Level Two.

Lightened image of first side of Stone 2 of Level Two.

Stone 2 of Level Two.

Original image of second side of Stone 2 of Level Two.

Lightened image of second side of Stone 2 of Level Two.

Stone 2 of Level Two.

This is an example of a stone which, when polished, fulfilled the promise it showed when first picked up off the beach.

Beginning of Alert Level Two, Thursday 14 May – Stone 1, Quartz from Gemstone Beach

To mark the move of New Zealand to Covid-19 Alert Level Two from Level Three, I am posting a Stone of the Day. This is despite today being a Thursday, and this series being posted on Mondays, Wednesdays and Saturdays. But I deem this to be an important day, with the lifting of a number of restrictions. And this is a worthy stone for the day. New Zealanders have waited patiently for Level Two for more than one and a half months.

Stone 1 of Level Two, polished quartz stone from Gemstone Beach.

One side of Stone 1 of Level Two.

Other side of Stone 1 of Level Two.

Stone 1 of Level Two.

I found this stone on Gemstone Beach last year and finished polishing it just a few days ago. It is a white quartz stone. At the beginning of my stone collecting, about four years ago, I used to collect a lot of white quartz stones. They catch the eye on the beach, standing out because of their brilliant whiteness. I found that my eye was automatically drawn to them, at the expense of other stones. I now have a nice collection of polished white quartz stones. But after a while I stopped collecting them, resisting their allure so that I could focus on other types. However, every now and then I come across an exceptional white quartz, worthy of adding to the collection bag.

Close up of Stone 1 of Level Two.

Close up of Stone 1 of Level Two. Tiny embedded black specks apparent.

Percussion plane in one side.

This white quartz stone is exceptional for three main reasons, size, shape and clarity. First of all, it is a largish stone, at the boundary of the size that can easily be tumbled in a 4 lb barrel. I recently purchased a 12 lb barrel, mainly to be able to polish larger stones. This enabled me to polish this stone without trouble.

Number of stones in a 3 lb barrel. Usually about 40-45 of them.

Number of stones in a 4 lb barrel. Usually about 100-115, depending on their sizes. Some slightly larger stones possible.

Number of stones in a 12 lb barrel. Usually about 180 to 200, depending on their sizes. Larger stones possible.

12 lb barrel on left, two 3 lb barrels on right.

Secondly, the stone is pendent-shaped, a symmetrical elongated oval. This is unusual, most quartz stones being asymmetrical in shape unless they are spheroid. Thirdly, this stone is unusual due to the amount of clear quartz in it. The whiteness in quartz is caused by the presence of water, giving rise to white cloudiness. The vast majority of beach quartz is fully white. This stone has some white but has just as much clear quartz, making it translucent and giving it a striking appearance.

Stone 1 of Level Two.

Looking into Stone 1 of Level Two.

Stone 1 of Level Two.

Looking into Stone 1 of Level Two.

There are two “imperfections” in the stone. On one side there is a scarf of percussion, a plane of breakage into the stone a small way. And there are a small number of tiny black specks embedded within it.

LDOL3 Stone #2, Wednesday 13 May 2020

Last Day of Level 3, Stone #2, is the end of a very brief series of recently polished stones from TumbleStone. It was intended that Posts would be made every Monday, Wednesday and Saturday throughout what remained of Covid-19 Alert Level 3 in New Zealand. The Prime Minister announced two days ago that the country will move to Alert Level 2 at midnight tonight.

In New Zealand’s Alert Level system, Level 4 “Eliminate” involved a national lockdown – “Stay at Home” – to minimise cases and prevent further transmission of the virus. New Zealand was in Level 4 from 26 March to 28 April. Level 3 “Restrict” involved only a minimal easing of restrictions – “Stay Safe” – in order to restrict any further outbreaks. And Level 2 “Reduce” involves easing of many economic, travel and social restrictions but with social distancing and hygiene guidelines – “Play it Safe”. I have taken the opportunity to arrange a stone collecting trip by car (and Cook Strait ferry) to the bottom of the South Island in a couple of weeks’ time.

LDOL3 Stone #2 is a recently polished white stone from Gemstone Beach. It could be a quartzite as it has clouds within it as many quartzites tend to, but I cannot be sure of its identity.

Polished white stone from Gemstone Beach.

One side of Stone 2 of Level 3.

Other side of Stone 2 of Level 3.

Size of Stone 2 of Level 3.

On the beach, it looked like an off-white stone with some vague patterns just visible. Tumble polishing has brought out the complex intricacies of its construction.

Detail of Stone 2 of Level 3.

In a recent Post, “Producing the Photos of the Stones of the Day“, I discussed aspects of photographing polished stones and using the Picasa app to “enhance” images to bring out patterns within the stones. The images below illustrate the stages involved in this for Stone 2 of Level 3.

Side 1, original image.

Side 1, image “saturated”.

Side 1, saturated image with “highlight”.

Side 2, original image.

Side 2, image “saturated”.

Side 2, saturated image with “highlight”.

This is how the “detail” of the stone was produced:

The original image of the stone was cropped to produce this.

“Saturation” and “highlighting” produced this version.

The original image of the stone was cropped to produce this.

“Saturation” and “highlighting” produced this version.

Helen’s Stones, Collected from Gemstone Beach, February-March 2020

From left: Ray (Helen’s husband), Petra, and Helen (picjing up a stone) on Gemstone Beach, 28 February 2020.

People on Gemstone Beach, just out from the carpark, 9 March 2020.

In February-March this year, I visited the beaches at Riverton and Orepuki to collect stones – this was just a few days before the Covid-19 Lockdown. I was often accompanied on my trips to the beaches by my sister Helen, sometimes also by my wife Petra and brother-in-law Ray. Petra and Helen also collected stones. Helen generously handed on to me most of the worm cast stones she found. She accumulated a number of interesting stones from Gemstone Beach for me to polish for her. I brought these home to Whanganui and put most of them into a 4 lb barrel. They spent seven days in a 320 grit tumble in late March, followed by a three hour tumble in Sunlight soap. They then tumbled in tin oxide Pre-polish for eight days in mid April, followed by a two hour soap tumble. Finally in late April they underwent ten days in tin oxide Pro-polish followed by one day in borax to complete the polishing process. Below are the 121 polished stones:

All 121 polished stones in a pile.

Close-up of some of the 121 stones.

There are some stunning stones in this batch. Helen and I spent some time after each day’s stone collecting going though her stones, evaluating each pebble before deciding to keep it for polishing or to discard it (in the garden at Helen and Ray’s Riverton crib). Any stone that was kept was likely to be interesting.