What kinda stone is this?

Loos like a common vitrified bond synthetic as far as I can see. Most likely aluminum oxide from what I can tell of the color.
 
Thanks. It’s not uncommon or anything special?

Would it sharpen a harder steel than an Arkansas stone would?
 
Yes, aluminum oxide and silicon carbide abrasives are MUCH harder (and sharper) than silicon dioxide (Arkansas stones/quartz) is. It doesn't appear to be an uncommon or especially notable stone. However its behavior may be different from other vitrified bond synthetic stones simply because there are many variables that go into them. The cut speed, finish produced, and the best degree of pressure to apply to it can all be impacted by the specific formulation of the stone.
 
FortyTwoBlades said:
Yes, aluminum oxide and silicon carbide abrasives are MUCH harder (and sharper) than silicon dioxide (Arkansas stones/quartz) is. It doesn't appear to be an uncommon or especially notable stone. However its behavior may be different from other vitrified bond synthetic stones simply because there are many variables that go into them. The cut speed, finish produced, and the best degree of pressure to apply to it can all be impacted by the specific formulation of the stone.
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To add to that: the surface preparation of the hone itself in the case of India, or aluminum oxide hones also plays a role in those characteristics. That is because the hones are generally not very friable and will hold their shape for quite a while. Most silicon carbide hones are quite a bit more friable and will more readily break down to an equilibrious state of coarse/fineness - that is to say, always pretty quickly settling back to the same place whether one should try to lap them coarser or finer.
 
Thanks for the info that helps me to understand what the best uses for it will be.
 
eKretz said:
To add to that: the surface preparation of the hone itself in the case of India, or aluminum oxide hones also plays a role in those characteristics. That is because the hones are generally not very friable and will hold their shape for quite a while. Most silicon carbide hones are quite a bit more friable and will more readily break down to an equilibrious state of coarse/fineness - that is to say, always pretty quickly settling back to the same place whether one should try to lap them coarser or finer.
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As further explanation, this is a result of both the bond strength and the friability of the grains themselves. Older oil stones tend to have a very hard bond to them and silicon carbide grains are more friable than aluminum oxide generally is. That being said, not all aluminum oxide stones are hard, per se, but hard stones do tend to exhibit a greater change in their performance characteristics dependent on their surface conditioning compared to more friable/softer bond stones.
 
FortyTwoBlades said:
As further explanation, this is a result of both the bond strength and the friability of the grains themselves. Older oil stones tend to have a very hard bond to them and silicon carbide grains are more friable than aluminum oxide generally is. That being said, not all aluminum oxide stones are hard, per se, but hard stones do tend to exhibit a greater change in their performance characteristics dependent on their surface conditioning compared to more friable/softer bond stones.
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Once again you are correct. I find that is pretty often the case with you. :D

My commentary was mainly regarding vitrified India hones, which I have found to be pretty uniform in that respect.
 
This may sound a bit odd, and it depends to some degree on how dirty or well-oiled a stone might be. But I've noticed over some time that natural stones, like Arkansas, actually have an earthy, sandy, soil-like smell to them. Same as if you'd picked up a rock off the ground and sniffed it - especially when it's wetted with some water. Synthetics, like AlOx and SiC, don't smell the same way.

At the dimensions posted for your stone (4" x 1" x 1/4"), I immediately thought of a small Norton India (Fine) stone I have, at the same dimensions. And the appearance of the stone and the apparent uniformity of the grit color & lack of obvious 'grain' or patterning suggest a synthetic stone to me, like a lot of common pocket/field stones in AlOx (aluminum oxide), including the India stones.

If you find over time, that the stone will cut some more mid-grade wear-resistant steels pretty easily, leaving obvious swarf on the stone, that also strongly suggests a synthetic stone. Natural/Arkansas stones will struggle to cut steels like 440C, 154CM, VG-10, D2, etc. Blades in such steels will feel like they're just 'skating' over the abrasive on a natural stone, without doing much, if any real cutting of the steel. Part of all this depends on how clogged, worn or glazed a synthetic stone might be - a very clogged or glazed aluminum oxide stone will struggle to cut much of anything. Very cheaply-produced aluminum oxide stones can glaze very quickly, meaning the grit at the surface becomes polished and will reflect light like glass does, when viewing from a low angle with bright lighting behind it.
 
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Thanks all for the replies. I don’t have any of the harder steels. 1095, case and buck stainless.

The person that gave it to me knows nothing about stones or where the stone came from.

So it’s likely a fine India stone. I mostly haven’t used it. I have used it a few times to try it out but so far it hadn’t fit into what I normally need.
 
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