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Green Stones and Microscope ID-ing

One of my favourite finishing stones, both because of how good it is, and because it's quite pretty, is a mysterious aqua coloured slate I picked up in the UK last year. There are some aspects of it that are similar to Glanrafon stone, while others including appearance are different. Nevertheless I suspect the stone is Welsh - if it's not a type of Glanrafon then probably quarried quite nearby.

And on arriving back home to Aus the other day I noticed something else interesting about it... I already had one. The previous stone was an Aus ebay purchase in the middle of last year, and though the cool wavy line patterns on the surface aren't quite as pronounced it's almost certainly the same thing, to my eye anyway.

So later I thought I'd have a look at them under a scope to confirm, along with a known Glanrafon, to see if there are any notable differences at a very fine level.

Top to bottom; AusBay stone, UKBay stone, Glanrafon:

IMG-4412.jpg


I'm just using an inexpensive USB scope here, with digital magnification up to 600x. It's not perfect, but will give good idea especially when compared in the same light, at the same magnification against an already id-ed stone. Having lots of things to compare is good, so I'm also going to snap shots of a load of other mostly green stones at the same time (the pic below is dry, so the stones look a little less green). Excluding the novaculites all of these stones have been finished at 1200 WnD.

Top; Glanrafon, UKbay, AusBay, Mystery Purple n Green Slate, Moughton, Green Thuri, Green Thuri, Charnley, Charnley.
Bottom; Mystery Green-Grey Stone, Grecian, Idwal, Gwespyr, Turkish, Chinese slate.

IMG-4397.jpg


Will post the results later, I shan't bore people with pictures of all of them, just any that are particularly notable...
 
That is one helluva nice looking collection right there. Those Glanrafon stones are beautiful! What is that Moughton stone? Where is it mined, and what are the qualities like? Wow, what a neat looking stone...
 
That is one helluva nice looking collection right there. Those Glanrafon stones are beautiful! What is that Moughton stone? Where is it mined, and what are the qualities like? Wow, what a neat looking stone...

Ah cheers, some lookers in there aren't there :).

Like the majority there the Moughton stone is a historic British stone, specifically from Yorkshire. Not a massive amount is known about it, other than it was apparently popular with the nearby Sheffield cutlery and razor industry. I'm not geologist so this is just a best guess but... while most of the stones in that pic above are slates or novaculites, the Moughton stone I don't think is a slate. I'd call it a mudstone/siltstone/shale (all kind of the same thing), and because of that it actually reminds me more of a Japanese stone than it does many European stones.

It also means that it can be soaked; slates are very bad at being soaked - they're very waterproof if you try to go through the layers, hence you can make roofing from them, but very porous between the folliated layers or cleavage, so water can get in and break the stone up as it dries. If you have a sedimentary rock like a shale, then as long as the layers aren't too pronounced they can work better as soaking stones as they'll dry more evenly.

Which is handy for the Moughton stone as it's not the quickest stone in the world and doesn't slurry that easily, and soaking a stone should make it softer and faster. It's not as fine as most of the other stones there, perhaps 6-8k in terms of actual particle size, but the action is far more of polishing and refinement than cutting so the effective finish is probably considerably higher.

And obviously... it's incredibly pretty!

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If you've not read them then this set of papers written by a Dutchman called Henk Bos are a superb work of scholarship concerning historic European natural whetstones: Index website Henk en Ge Bos - https://bosq.home.xs4all.nl/
 
Here then are a few of the scope shots with a little bit of insight...

This is the larger Charnley, and a fairly typical example of what quite a pure and fine novaculite looks like. Trans arks look very similar to this:
LargeCharn.jpg

Turkish (this is a very fine Turkish). The 'grit' is almost but not quite as fine as the Charnley, but with a load more sparkly abrasive to it:
Turkish.jpg

Small and large Green Thuris. From these images they might as well be the same stone. This is what very fine shale-slate looks like. What's notable about this is a quite high silica content for something so fine:
SmallThuri.jpg
LargeThuri.jpg

Glanrafon. A little less fine than the Thuris but not by much. Markedly less silica:
Glanrafon.jpg

And our two Mystery Aqua-coloured stones, small one from Aus and then large from UK. These stones are very clearly the same thing, and they're not the same thing as the Glanrafon. They're a little finer and more compact, with maybe a slightly higher Silica content, especially the smaller:
MysteryGreenSmall.jpg
MysterGreenLarge.jpg

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So there you go.

I don't know if it said much that I couldn't have guessed with them in hand. But it's a cast iron confirmation that my new 10x2 is a green Thuri, and that the two Mystery Aqua stones are the same as each other, but they're not Glanrafons. Perhaps the most surprising thing here for me is just how fine and pure a novaculite the larger CF is.
 
One of my favourite finishing stones, both because of how good it is, and because it's quite pretty, is a mysterious aqua coloured slate I picked up in the UK last year. There are some aspects of it that are similar to Glanrafon stone, while others including appearance are different. Nevertheless I suspect the stone is Welsh - if it's not a type of Glanrafon then probably quarried quite nearby.

And on arriving back home to Aus the other day I noticed something else interesting about it... I already had one. The previous stone was an Aus ebay purchase in the middle of last year, and though the cool wavy line patterns on the surface aren't quite as pronounced it's almost certainly the same thing, to my eye anyway.

So later I thought I'd have a look at them under a scope to confirm, along with a known Glanrafon, to see if there are any notable differences at a very fine level.

Top to bottom; AusBay stone, UKBay stone, Glanrafon:

View attachment 1395004

I'm just using an inexpensive USB scope here, with digital magnification up to 600x. It's not perfect, but will give good idea especially when compared in the same light, at the same magnification against an already id-ed stone. Having lots of things to compare is good, so I'm also going to snap shots of a load of other mostly green stones at the same time (the pic below is dry, so the stones look a little less green). Excluding the novaculites all of these stones have been finished at 1200 WnD.

Top; Glanrafon, UKbay, AusBay, Mystery Purple n Green Slate, Moughton, Green Thuri, Green Thuri, Charnley, Charnley.
Bottom; Mystery Green-Grey Stone, Grecian, Idwal, Gwespyr, Turkish, Chinese slate.

View attachment 1395003

Will post the results later, I shan't bore people with pictures of all of them, just any that are particularly notable...
get ya a vermont green slate
 
This is the green unknown I have like yours under the loupe iphone pic. I don't have a scope so the best I can do.

View attachment 1395537


It's still quite an impressive amount of detail for an iphone pic. Is this just holding a loupe up to an iphone camera? cos if so that's rather a neat trick!

I looked at various parts of the GR stone (all the different colour sections), and it was definitely different from the aqua stones. Similar, but different. The search continues...
 
The other thing I should point out about the pictures above is that they're of three different types of stone...

The Thuris actually look a little less fine than the Aqua stones and certainly less fine than the CF, even though actually finer than both. This is one of the slight drawbacks of trying to analyze something solely based on scope pics - you need to have an understanding of what type of material you're looking at, or at least how hard it is. Because if the structure of something is very tight and dense then it's going to appear finer.

Thuris are often described as slates, but if they are then they're only just, with very light metamorphic change (hence the lack of much noticeable folliation or cleavage). I'd probably err on the side of describing them as shales or mudstones, under a scope the structure is more similar to some very fine jnats.
 
It's still quite an impressive amount of detail for an iphone pic. Is this just holding a loupe up to an iphone camera? cos if so that's rather a neat trick!

I looked at various parts of the GR stone (all the different colour sections), and it was definitely different from the aqua stones. Similar, but different. The search continues...
Yup I just put the iPhone camera up to the loupe. I think this was the loupe that has a light on it.
 
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Yesterday I did something that I'd been meaning to do for a while and I bought a Dragon's Tongue stone from Inigo Jones. And then I emailed them, on the off-chance that someone there might know something about my mysterious and beautiful Blue-green stones. I'd read before that one of the directors - Roger - was incredibly knowledgeable about this kind of thing. Now in his mid-70s, and having worked in the Welsh slate industry for more than half a century, our man clearly knows what he's about, and replied a couple of hours later to tell me this:

'The Green one comes from the Nantlle Valley where there used to be several quarries operating but now all closed, one quarry was called the Dorothea quarry and that slate might have come from there.'

The Nantlle Valley (Dyffryn Nantlle) is in the west of Snowdonia National Park, set around a lake of the same name - Llyn Nantlle. What was particularly interesting about this news is that the Glanrafon quarry lies just to the north of the small village of Rhyd-Ddu, which is at one end of the Dyffryn Nantlle. Dorothea is at the other, with a few more small quarries in between we might imagine. Though the valley isn't big in the grand scheme of things - from Dorothea to Rhyd-Ddu is just five miles.

So when we speculated in the post above 'if it's not a type of Glanrafon then probably quarried quite nearby', it was spot-on. The two stones are very similar slates, from the same bed of rock.

Though I don't believe them to be exactly the same. Both are hard, fine and slow. Though the blue-green stone seems marginally finer in use, which appears to be corroborated when looked at under the scope, at least in my examples. And they don't look all that similar; they look similar enough that it's possible they came from the same quarry, though the Glanrafon stone is more patterned. And perhaps the kicker is how they're cut: the Glanrafon stone seems always to have been cut with the original bedding planes running across the width of the hone, whereas for the blue-green stone they run parallel to the length. These are both slates, so it doesn't really make any difference apart from visually, but it's worth noting.

So I think we'll call this stone the Llyn Nantlle.*

@rideon66 , who's the only other person I know to have an example of this stone, found a picture of slate from the Dorothea quarry, and I think it likely to be the origin of the stone. Though if we call it the Llyn Nantlle that'll cover our bases, if perhaps it was from one of the other small quarries set around Lake Nantlle. And most of the other historic Welsh hones seem to have been named after lakes, so we'll roll with tradition.

My stones:

IMG-5315.jpg


Rideon66's:

Greenunknown8.jpg




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So there's my little contribution to the pool of knowledge regarding historic UK sharpening stones. There are hundreds of old types of UK whetstones from disused quarries, where information about them has simply died out over the years. It's just lucky in this instance that there are still some old-timers like Roger left around with the breadth and depth of knowledge to be able to help.

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* Welsh names like this can be rather difficult for a lot of people (myself included) to pronounce properly, as it involves sounds that are not used in the English language. But if you wanna give it a go... this is how to say Llyn and Nantlle in Cymraeg.
 
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Also - though the stone seems to be relatively uncommon, there are clearly examples to be found out there. One of my Llyn Nantlles came from the collection of someone in Norwich who had an insane amount of high quality UK stones. Though the other was a mystery stone purchased on Australian Ebay six months before, so they were clearly regarded as good enough to warrant importing half way around the world. And I'd certainly recommend anyone to snap up a LN if they come across one ever.
 

Legion

Staff member
Also - though the stone seems to be relatively uncommon, there are clearly examples to be found out there. One of my Llyn Nantlles came from the collection of someone in Norwich who had an insane amount of high quality UK stones. Though the other was a mystery stone purchased on Australian Ebay six months before, so they were clearly regarded as good enough to warrant importing half way around the world. And I'd certainly recommend anyone to snap up a LN if they come across one ever.
I’m guessing if I ever find one it will be more through luck, and I won’t know it until after it’s cleaned. But at least you will have solved the mystery for me.
 
I’m guessing if I ever find one it will be more through luck, and I won’t know it until after it’s cleaned. But at least you will have solved the mystery for me.

My smaller one was certainly pretty much impossible to see the pattern and colour of before I'd given it a good clean and lapping.

Though from memory the seller was in VIC, so keep yer eyes peeled!
 
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