Stones Under The Microscope

[cotedupy]

I did a cursory search but couldn't find a thread on this, so thought I'd start one. And if others in possession of similar gizmos want to add, it might turn into a nice resource.

Recently someone kindly lent me their USB microscope thing. Nothing fancy, and it perhaps doesn't go up to the level to really properly be looking at the finer details of edges, but it seems quite good for stones. So I thought I'd have a look at some of mine, particularly some of the ones in this thread here: Some old stones arrived today (a two-part thread) - https://www.badgerandblade.com/forum/threads/some-old-stones-arrived-today-a-two-part-thread.609907/

These pictures are somewhere between 500-600x, which is as high as this scope goes. Note also- I've not done this before about half an hour ago, so my conclusions / thoughts are completely amateur. And that the colour of the stones probably doesn't mean much I imagine, I'm looking more at the grain.

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Starting with novaculite, here's a bit of Translucent Ark which is highly homogenous as you'd expect:

This is the Llyn Idwal/Grecian in my thread linked to above. Much looser more heterogenous grain structure:

This is the possible Charnley Forest, or finer Llyn Idwal. Which looks pretty similar but maybe slightly tighter structure:

Now let's look at my old Turkish Oilstone. Back to a more homogenous structure than the UK stones, but not as fine as the trans ark, though it has other areas that have inclusions and stuf that you often get in old Turkish stones. This stone cuts far quicker than any of the previous:

And now the reason I started this rather geeky experiment in the first place, the mystery black stone from the link above. This stone looks in the flesh like it could be another Turkish, and it smells identical to the above, but in use it's very different - this is the finest of all these stones, and very hard / dense. And under the scope it's completely different; far more heterogenous than any of the above despite being finer, I'm now fairly confident this stone is not novaculite:

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I'll add further pictures of other stones, but anyone else do please add if you technology and inclination...

 

[cotedupy]

Now let's look at some slates. You can clearly see the distribution of quartz within the shale-type bind. Though unfortunately the mystery stone above doesn't look much like slate either.

This is a Welsh Purple:

A Chinese slate, clearly finer than the above:

And an Australian slate from Willunga, more similar to the Welsh slate, but seemingly with less quartz, which perhaps explains why this stone is quite slow:

 

[cotedupy]

And some interesting ones, that show both the advantages of looking at stones in this way in terms of identification. But also the drawbacks if trying to draw any qualitative conclusions about how a stone might act...

This is an old Coticule:

And this is a Hindustan. These possibly don't get talked about much here (or anywhere really), so for those that might not know - it's a type of sandstone from Indiana, US. In terms of particle size and distribution this isn't a million miles away from the coticule, though the composition of the stone is far more heterogenous, and in use far coarser than the coti. Which perhaps underlines the uniqueness of the way in which coticules work in terms of bind and slurry breakdown of garnet - the Hindustan like most stones has quartz as an abrasive:

Let's go proper niche... this is a Finnish stone, a Wästikivi. This stone looks incredibly coarse by comparison, but might actually be a comparable grit level to the Hindustan, c. 1-3k. Wästikivi are phyllite, a kind of slate that has undergone further metamorphic change leading to the formation of larger visible micas, which is why the stone looks so coarse. Though mica is obviously far softer than quartz, so won't affect the sharpening or effective 'grit' of the stone:

This next stone is possibly another Hindustan, though I've always had my doubts about that. It person it looks and behaves quite differently from the previous one, and under the microscope the micas make the stone look more similar to the Wästikivi. I don't know what this stone is, but someone recently sent me a video of an old Pike stone mined in New Hampshire - the Lisbon Chocolate Hone - a kind of mica and quartz heavy schist, which looked similar. I've never handled one, but if I was told that's what this stone was, I'd believe it.

And last up, a branded Norton Hard (Translucent) from the late 1950s. I terms of purity this is not as fine as the translucent in the previous post, but as a stone I prefer it. In use it is no less fine, but cuts slightly quicker:

 

[malocchio]

Thanks for posting, really fascinating !

 

[Toro Blanco]

Qualitative can be done and depends on the users experience in the subject and his/her ability to interperste the information givin. That will determine how usefull the information is.

Quantitative is the scientic one that costs crazy money but is the only way to prove anything. Everything else is qualitative.
I took research science courses in 2004 so that is right up my alley. Most get it confused and try to sound smart and know it all but in a research setting would get laught at by the whole class. I have seen it many times.

What you are doing cotedupy is actually usefull especially when you are getting into different kinds of sharpening stones or media.
I would say it is a good learning experience.

 

[cotedupy]

Qualitative can be done and depends on the users experience in the subject and his/her ability to interperste the information givin. That will determine how usefull the information is.

Quantitative is the scientic one that costs crazy money but is the only way to prove anything. Everything else is qualitative.
I took research science courses in 2004 so that is right up my alley. Most get it confused and try to sound smart and know it all but in a research setting would get laught at by the whole class. I have seen it many times.

What you are doing cotedupy is actually usefull especially when you are getting into different kinds of sharpening stones or media.
I would say it is a good learning experience.

Indeed! I meant more that at 500x magnification I couldn't look at two unknown stones (eg. if I didn't know what the the Coticule and Hindustan above were), and tell you about how the bind and slurry is going to work in use, or that one has a load of garnets in it and the other doesn't.

But I can look at what I assume is mica (and possibly feldspar?) formation in the second mystery stone, and say that I don't think it's a Hindustan, I think it's a schist. Or indeed that the first mystery stone is pretty evidently not novaculite, but I wouldn't have been able to say that it was clearly finer in use than the novaculite stones above it.

I assume that kind of thing does become more possible at higher magnification, or indeed if you took two known stones of the same type you'd be able to make reasonable guesses about their behaviour, from the comparisons.

(Feel free to tell me that any, or all, of my comments are nonsense btw! And if you have any ideas regarding the stone I don't know in the first post I'd be very keen to hear them. It's completely flummoxed me so far...)

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Next up will be some jnats...

 

[Toro Blanco]

I agree with your comments.

I will add this help the best I can.
When you take a class on how to use a microscope is, it is all about clarity not magnification.
They beat it into your head over and over. They have set up example after example to prove to you that it is true, everything else being equal.
Magnification is needed but always emphasize it is always secondary to clarity.
That is why I stress to everyone that wants to do grit evaluation or edge comparison. That the only way you will do this is with a quality microscope.
They even go as far as saying that most research science facilitys pretty mush use two brands Zeiss and Leica. Olympus is a distant category. They are used more for optical comparators that need quality optics but not the best.
Ever wonder why top notch camerras have Zeiss or Leica apertures. In the end that is what you are paying for is the aperture the rest of the microscope is relatively inexpensive. Its all about the aperture.
Same with the microscopes, you can see good detail with a 300$-500$ microscope but use a Zeiss or Leica and you mind will be blown away with what you can see with high quality instuments.
They are expensive but buy the best you can afford as it does help you see what others can only dismiss because they cant see it. Light manipulation is extemely important as well.
That is what makes the difference between a metallurgical microscope and a regular one. Top notch ones have a light refracter instead of a light diffuser. Basically a quarts crystal and light source on top of the work surface rather than onthe bottom going through some whiteor clear plastic.
If you know what you are doing you can make your regular microscope act like one used specifically for looking at metal samples and stones like we need to look at edges and stones.

Like my teacher would say you can see good with others but you cant see what I can see. Lol! She was a top notch research scientist that testified as a expert wtness in SCOTUS cases. That should tell you something, Top notch.

P.S. a way to get quality microscopes is if you live near a university if look on local means like craigslist as students often sell very good microscopes a bottom dollar. You can find some crazy deals by starving students that could not hack it in school and just try and get whatever they can for it.

 

[cotedupy]

On to a handful of Toishi... Now in terms of geological formation and basic abrasive composition most Jnats are on the same page as many other sharpening stones in the world; lithification and metamorphic change of some kind of deposited 'mud', with SiO2 / quartz in it. About a billion factors affect the way a particular stone might feel or work, but that's the gist. And again a lot of those things are going to be pretty tricky to decipher from USB microscope images, but let's have a look...

(I'm going to give vague guesses as to approximate 'grit' levels, rather than some of the other rating systems. Cos I don't know half of them.)

Here's a Morihei brand Binsui (sandstone) it's much coarser than the subsequent stones at around 1k. You can see the random scattering of different size particles and minerals. This stone is quite soft, if it were harder the effective grit level would be higher I think.

These next two are Suita, first a Shobudani which is probably around 5-6k. You can see some karasu pattern, and in the top right part of a suji line. The particles are not entirely uniform in size here.

Here a Maruoyama Shiro Suita. This is a smidge finer at around 7-8k, and you can probably just about see that here, though they're quite similar. Again I've included a non-toxic suji. Both of these suita are on the soft side of medium, and slurry nicely. This is a lovely stone:

Now a Nakayama, I don't know the layer. It's harder than the two suita, and a bit finer than the Maruoyama - around 9k. Particle distribution looks very compact and uniform:

Now two Tomae, this first is a Shobudani. Stone looks notably coarser than the two suita, but it's also harder - in terms of effective finishing 'grit' this is comparable to the Maruoyama, though the edges are different.

And last up an Okuda Tomae. This has all sorts going on, and I don't know what much of it is. Like the Nakayama - individual silicate particles are becoming hard to distinguish though - this stone is very hard even by the standards of jnats, and *very* fine. We're up well north of 10k with this stone:

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As a disclaimer - I know even less about Japanese stones than I do about others, so god knows if any of my guesses / summaries are in any way correct.

 

[cotedupy]

I agree with your comments.

I will add this help the best I can.
When you take a class on how to use a microscope is, it is all about clarity not magnification.
They beat it into your head over and over. They have set up example after example to prove to you that it is true, everything else being equal.
Magnification is needed but always emphasize it is always secondary to clarity.
That is why I stress to everyone that wants to do grit evaluation or edge comparison. That the only way you will do this is with a quality microscope.
They even go as far as saying that most research science facilitys pretty mush use two brands Zeiss and Leica. Olympus is a distant category. They are used more for optical comparators that need quality optics but not the best.
Ever wonder why top notch camerras have Zeiss or Leica apertures. In the end that is what you are paying for is the aperture the rest of the microscope is relatively inexpensive. Its all about the aperture.
Same with the microscopes, you can see good detail with a 300$-500$ microscope but use a Zeiss or Leica and you mind will be blown away with what you can see with high quality instuments.
They are expensive but buy the best you can afford as it does help you see what others can only dismiss because they cant see it. Light manipulation is extemely important as well.
That is what makes the difference between a metallurgical microscope and a regular one. Top notch ones have a light refracter instead of a light diffuser. Basically a quarts crystal and light source on top of the work surface rather than onthe bottom going through some whiteor clear plastic.
If you know what you are doing you can make your regular microscope act like one used specifically for looking at metal samples and stones like we need to look at edges and stones.

Like my teacher would say you can see good with others but you cant see what I can see. Lol! She was a top notch research scientist that testified as a expert wtness in SCOTUS cases. That should tell you something, Top notch.

P.S. a way to get quality microscopes is if you live near a university if look on local means like craigslist as students often sell very good microscopes a bottom dollar. You can find some crazy deals by starving students that could not hack it in school and just try and get whatever they can for it.

Yeah I can certainly imagine this being the case. For this little USB one it's tricky enough getting the focus / clarity to this level. I assume because it's using a degree of digital magnification(?). Though it's giving I think a reasonable general impression of the stone - especially for the two I didn't know above - aspects of the structure there were completely invisible to the eye.

And interesting to see just how homogenous and fine translucent arks are compared to other novaculite.

 

[Toro Blanco]

For what you are using it for it is more than adequate. I did something similar when I started with stones. They have a light on top and that helps a lot.
Back in 2004 the best usb was like 1.2 mp and my teacher had just got her hands on a brand new 2.l mp. Lol!
It is good enough as we used it to connect to a projector so the whole class can see what was going on.
A little trick to get the most out of usb is connect it to a 50" or 60" digital television. I have seen this done in clean rooms in silicon valley so I know it is a good thing. They were impressed that I knew about it as they were touting it a cutting edge at the time and this was a satelite company that put their products in orbit.

For stone evaluation you don't need super fine detailed resolution as you have come to find out. It give enough resolution in order for you to make a qualitative assesment.
The more you use it the more you train your brain to understand what your eyes are seeing. Your brain has to learn to interperate this new information and the only way to do that is by looking at more and more samples.

 

[FarmerTan]

VERY educational thread my friends! Following with interest...

 

[cotedupy]

For what you are using it for it is more than adequate. I did something similar when I started with stones. They have a light on top and that helps a lot.
Back in 2004 the best usb was like 1.2 mp and my teacher had just got her hands on a brand new 2.l mp. Lol!
It is good enough as we used it to connect to a projector so the whole class can see what was going on.
A little trick to get the most out of usb is connect it to a 50" or 60" digital television. I have seen this done in clean rooms in silicon valley so I know it is a good thing. They were impressed that I knew about it as they were touting it a cutting edge at the time and this was a satelite company that put their products in orbit.

For stone evaluation you don't need super fine detailed resolution as you have come to find out. It give enough resolution in order for you to make a qualitative assesment.
The more you use it the more you train your brain to understand what your eyes are seeing. Your brain has to learn to interperate this new information and the only way to do that is by looking at more and more samples.

The main question I'd have about this kind of analysis is how you would go about interpreting the bind...?

I also don't know to what extent that affects razors. I sharpen knives in a kinda professional capacity, and the bind has a *huge* effect on the relative grit levels of stones, and the outcomes... I can make a knife incredibly sharp on a pretty coarse stone, if it's hard enough. If a stone is soft then it really needs to be either very even or very fine; the Binsui above for instance is pretty shoddy tbh. But I don't know how much that kind of thing extends to razor honing?

It's also obviously a slightly different world, because razor honing is working at much higher grits generally. Beyond about 8k you're probably starting to negatively impact most kitchen knives in practical use, by overly refining the edge (imo), and usually I'd stop well before that.

 

[FarmerTan]

The main question I'd have about this kind of analysis is how you would go about interpreting the bind...?

I also don't know to what extent that affects razors. I sharpen knives in a kinda professional capacity, and the bind has a *huge* effect on the relative grit levels of stones, and the outcomes... I can make a knife incredibly sharp on a pretty coarse stone, if it's hard enough. If a stone is soft then it really needs to be either very even or very fine; the Binsui above for instance is pretty shoddy tbh. But I don't know how much that kind of thing extends to razor honing?

It's also obviously a slightly different world, because razor honing is working at much higher grits generally. Beyond about 8k you're probably starting to negatively impact most kitchen knives in practical use, by overly refining the edge (imo), and usually I'd stop well before that.

I wish I was as smart as you!

I'm just smart enough to pick up about 30 percent of what you are puttin' down!

 

[cotedupy]

I wish I was as smart as you!

I'm just smart enough to pick up about 30 percent of what you are puttin' down!

Haha... it is all slightly pointlessly geeky this thread! TBH - with the exception of the Turkish I don't really use any of the stones above in normal 'work' sharpening. I mostly use about 5 or so synthetics.

 

[cotedupy]

A few more pics of other stones, which again show I think both the advantages, but also some of the difficulties in analysing stones like this...

It was suggested in another thread that the coticule I pictured above looked like could also be a PDSO - there were quite a few things about it that made it tricky to say one way or another. So I had a look at it again:

And then at a different, definite coticule. I think it's fair to say these are the same type of stone!

And here's the naturally bonded BBW side of the second coti. You can see why BBW slurry is kinda purple; those red dots are all over the stone, to the naked eye they look like tiny black pinpricks. under the microsope this stone looks coarser than it acts.

Now a couple of Australian stones - these are shale/mudstone type things. This one is coarser:

This is finer. Neither of these look a million miles away from some of the Japanese stones above, especially the Suita. And in terms of composition they're probably quite similar. But the Australian stones are much softer/more loosely binded, and this makes them coarser and less consistent in use. The hardness of the bind is something I at least can't tell just from this kind of picture.

And lastly something a bit interesting. This is an old Japanese stone from the, now closed, Iyo mine. This stone is *very* slow in use - you can barely see any visible quartz particles, though it's not a high grit stone (3k maybe). This is an example of what sets some Japanese stones apart... it is a superb polishing stone, though if you're trying to set an edge, you'll get nowhere.