Thread: How do you test an unknown natural stone?

It is very simple.
finish your edge on an 8k then move on the unknown plain water and test if there is improvement. See what happens with using slurry.
If nothing happens then go higher 10-12k , do the same, this will help you zero in on the approximate fineness level.
After that you a re going to have to figure out the best procedure to get max of the stone.

I run the end of my fingernail over the stone , and see how it compares to a hone of a known grit rating . This will give me a "ball park" idea of what I'm dealing with .

If you suspect it's a finisher, the best way is, use your stones as you always do, and then, instead of the finisher stones you regularly use, finish it on your unknown stone. That's the procedure. The real test is, shave with it. You will like it, or you wont.
Another way is, find a shave ready razor or two, and then pass one a few times from the stone you don't know how fine it is. Strop and shave with both and compare.
If you don't know if it's a finisher or not, both the spoon test and licking the stone are very good tests. The water absorption test works for most stones. In the "I don't know the grit of a stone, that is actually a sharpening stone-hone" question, experience is a useful tool.
Now, if you really want to know if your stone is an actual Thuringian, there are ways, but you'd better not know about them, since it is very possible that you will destroy your stone.

Originally Posted by Vasilis

If you suspect it's a finisher, the best way is, use your stones as you always do, and then, instead of the finisher stones you regularly use, finish it on your unknown stone. That's the procedure. The real test is, shave with it. You will like it, or you wont.
Another way is, find a shave ready razor or two, and then pass one a few times from the stone you don't know how fine it is. Strop and shave with both and compare.
If you don't know if it's a finisher or not, both the spoon test and licking the stone are very good tests. The water absorption test works for most stones. In the "I don't know the grit of a stone, that is actually a sharpening stone-hone" question, experience is a useful tool.
Now, if you really want to know if your stone is an actual Thuringian, there are ways, but you'd better not know about them, since it is very possible that you will destroy your stone.

I want to know, I wont promise I'll try on my Thuris but it wont hurt to know a test

It's about its chalk and Silicon containing minerals content. Simple procedure, anybody with experience in Chemistry knows the rest. The bad thing is, we don't have enough data? (not sure if it's the correct word) about mineral concentrations on this type of stone, although it's unique.

Thanks for all the replies! I took a little of every body and this is what I ended up doing. I didn't cook the stone but while I was honing two razors from bevel to 8k I heated slowly the stone with tap hot water. Started with warm and in three stages ended with full hot tap water ( about 15 min). This was to bring the temp of the rock slowly so it would not crack.

Then I washed it with soap, water and old tooth brush. Rinsed well and lapped it with a well worn 325, then atoma 1200 (I suspect is a Turingian). Let dry and come to room temperature. Did a scratch test with nail. Took pictures, dry, wet and with slury. Here they are, the one in the wood narrow box, it's supposed to be a dark blue vintage Turingian.





Then I let the slury dry on top of the stone. Compare smell and tasted them with tongue ? I hope this is not one of those beginners prank! Took a very nice 8k edge, went to the 16k shapton and then water only on stone.

Here are the observations.

Color, texture and hardness appeared the same as the 1" dark Turingian. They both smell like river dirt, with a hint of iron somewhere. The taste on both, was tasteless. The slurry, was the only thing different. The known Turingian slury was very dark grey, giving a bluish hue to the milky slury, the unknown wider stone, was grey, bordering on light grey, giving a milky appearance to the slury.

Took a tpt and a hht test before the stone (after the 16k) and then, after the unknown stone. It felt as it didn't improved or degraded. The shave is tomorrow. I'll let you all know if it's a keeper or a dud, so far it looks promising. Double O

I say it's time to give it a name.

One more thing I've noticed with different stones is that some stones give you a slurry that will dry you skin out.
I don't know why but it sure can be used to distinguish some rock from others.
Sand stones are a prime example of it!

Originally Posted by Hirlau

I say it's time to give it a name.

"Turingian"? If it walks like a duck, quack like a duck, it's a duck! LOL! Double O

Originally Posted by Double0757

"Turingian"? If it walks like a duck, quack like a duck, it's a duck! LOL! Double O

Or just Mr T, to be on the safe side?

I've got a few "black rocks" I never got around playing with, that's why I looking for the "definite test", if there is one.
Tried one of them quickly and it cuts nicely and gives an edge on a CVH not far from my G/Y Escher, other than that it's just hard, dense and black as jet!