Thread: Comparison Sheet for Natural Stones?

I have been kicking around the idea of making a list of natural stones with an effective grit RANGE associated with them and maybe a few defining characteristics for each.....

My biggest problem is the fact that although I LOVE natural stones, I don't own many and I'm a poor judge of a stone's grit...which is why I started researching the grit comparison in the first place!

For example, I have seen the Coticule being listed as similar to an 8K hone, but others say maybe 6K for their particular stone and some say the edge they get is closer to 10K....so I was thinking of going with something like this...


Stone Name/Type - Minimum grit seen - Max grit seen - Water or Oil - Origin

Coticule - 6000 - 10000 - Water - Belgium


Any thoughts on ways to change and improve the list?
How about helping with the grit ranges?


Here are the stones I have on the list so far...

Yellow Coticule
Belgian Blue
Thuringian
Charnley Forest
Cutler's Green
Water of Ayr
Tam O'Shanter
Dalmore Blue
Dalmore Yellow
Welsh Dragon's Tongue
Chinese Guangxi Hone
Queer Creek Stone
Roszutec
BM 6000
Schwedenstein
Silk Stone
Jasper
Chert
Flint
Obsidian
Jade
Wästikivi
Beryl
Soft White Arkansas
Hard White Arkansas
Hard Black Arkansas
Translucent Arkansas

Any suggestions would be appreciated!

It would be interesting but at the same time wouldn''t it be totally speculative ? I've seen threads with people getting into arguments over their claims for grit values of their chosen naturals.

it will be really hard to get accurate data.japan hones etc how would you grit them? will be confusing in the other hand there is not exact grit same name brand natural hones available. they differ among them.example 2 yellow green escher's will not have exact grit size.

First of all people set bevels on a coticule with slurry, so its grit equivalence would be around 1k all the way through 12k? 30k? whatever you wanna call a final edge, and its actual grit is measurable (the size of the garnets) but unfeasible- and I promise will be almost nothing like its "grit equivalency". Also, you completely forgot Japanese naturals. And then you would need a wealth of things about the different colour stones. Which only seem to have minor differences. AND THEN you need to establish a common grit system for comparison. It would be better to use micron sizes to "compare" though this would be far less accurate scientifically.

I'm gonna get whaled on really hard for this next statement, because I have not honed with every single hone out there, but its pretty common knowledge that when you say 8k it doesn't mean anything unless you specify the system. So common you can call up the manufacture, ask for the MSDS and find out the grit size. Wusthof sells hones that run 800 1k 1200 2k. I asked them, turns out its in FEPA, or the rough equivalent of 1k 3k 5k 8k JIS (new). Norton doesn't use a standard system, Shapton also uses their own system. Naniwa is on JIS, as is Henckels. DMT uses mesh (micron sizing). If you disagree, go ahead and look up pictures of Shaptons. The Shapton 8k says in no uncertain terms 1.84 micron=8k. If you click here and scroll down you can see that Norton calls 3 micron 8k. You do the math. One thing to note is that this is the OLD JIS, the new JIS 8k is somethign like 1.2 micron. Gunner777 has a great chart already started with this kind of comparison.

All that said I think it would be a great idea if instead of grits/micron ratings we made a chart of how the stones are best used in a progression. For example a Thury fits better towards the finishing end.

Originally Posted by khaos

First of all people set bevels on a coticule with slurry, so its grit equivalence would be around 1k all the way through 12k? 30k? whatever you wanna call a final edge, and its actual grit is measurable (the size of the garnets) but unfeasible- and I promise will be almost nothing like its "grit equivalency".

You have to be more careful here; cutting speed and grit size are two totally different things. Using a slurry will not change the grit size (unless I am seriously misinformed about what slurry is), but will change the cutting speed. When you talk about grit equivalence, I think it is important to mention if you mean equivalent cutting speed or actual grit size (with respect to different ways of "measuring" grit size). Above, it looks like you are talking about cutting speed while in the second part of your post, you seem to be referring to the ways grit is "measured."

Just trying to be clear so no one gets confused.

Thanks for clearing that up... thats why I talked about "equivalence" and grit seperately. Sorry for the confusion.

its actual grit is measurable (the size of the garnets) but unfeasible- and I promise will be almost nothing like its "grit equivalency".

What I meant is the true grit of the stone, as in its cutting particle size, doesn't necessarily mean much when comparing two stones, or even the same stone under different conditions.

Beryl? Does anyone use beryl as a stone? it is basically emerald or aquamarine and often is found in large hexagonal crystals that are too full of crud or cracks to be of use to anyone exept as a source of beryllium. Wouldn't think it would be worth much as a hone.

Jade comes in two different types: nephrite (hardness 5.5-6) which is a massive form of the calcium-magnesium-iron silicate amphibole actinolite. And, jadeite a massive form of a sodium aluminum silicate pyroxine like olivine, peridot, orthopyroxine and diopside (hardness 6.5-7)... Jadeite is harder but nephrite is tougher Both can be polished fairly smooth but I don't think they have any set grain size.

Chert is what glues most sandstones and even arkansas stones together. It is basically quartz/silica, the same as agate, jasper, quartzite, opal,flint or novaculite etc. Silica is partially soluble in warm alkaline water and forms flocculant precipitates when the pH goes down. Hydrothermal action often partially dissolves sand (quartzite and sandstone), diatomacious earth (novaculite) and reprecipitates between the grains cementing them together, or silica laden waters dissolve and replace grains of carbonate or other mineral or form a dense cement around impurities (flint, jasper or agate etc). It varies like novaculite... the black stuff is full of manganese dioxide and dense chert cement around heavily dissolved diatom shells (which come in nearly every shape from little 5 micron balls to 200 micron long rods)... in the coarser novaculite stones the shells just less dissolved and not as heavily cemented together.

Obsidian is just glass. About 70% quartz contaminated with amphibols or other mafics (dark iron/magnesium rich minerals). It would be pretty much like sharpening on a hunk of plate glass (you could always use ammonium fluoride to etch the surface to whatever degree of "frost" you want)

What I'm looking for is carbonado, which are natural polycrystalline diamonds (no cleavage planes and a bit harder than regular diamond). They are believed to come from space NOVA Online | The Diamond Deception | Diamonds in the Sky for a pic of one.

Friend of mine lives in Belgium and his back step is a huge blue stone (yes he sharpens his kitchen knives on it)... heard them estimated to go up to about 4000 grit and the cotucules to range from 8000 to 12,000 but that is just what I've heard from others who've handled them.

Originally Posted by yuzuha

Beryl? Does anyone use beryl as a stone? it is basically emerald or aquamarine and often is found in large hexagonal crystals that are too full of crud or cracks to be of use to anyone exept as a source of beryllium. Wouldn't think it would be worth much as a hone.

Already pointed this out, turns out its good as a polisher according to some. I suspect this is because it was lapped smooth and its harder than steel, so like honing on plate glass.

Originally Posted by yuzuha

...jade...Both can be polished fairly smooth but I don't think they have any set grain size.

Once again, surprisingly its apparently a good polisher. Once again, I suspect it's because it was smooth and harder than steel. Like honing on plate glass.

Originally Posted by yuzuha

Chert is what glues most sandstones and even arkansas stones together. It is basically quartz/silica, the same as agate, jasper, quartzite, opal,flint or novaculite etc. Silica is partially soluble in warm alkaline water and forms flocculant precipitates when the pH goes down. Hydrothermal action often partially dissolves sand (quartzite and sandstone), diatomacious earth (novaculite) and reprecipitates between the grains cementing them together, or silica laden waters dissolve and replace grains of carbonate or other mineral or form a dense cement around impurities (flint, jasper or agate etc). It varies like novaculite... the black stuff is full of manganese dioxide and dense chert cement around heavily dissolved diatom shells (which come in nearly every shape from little 5 micron balls to 200 micron long rods)... in the coarser novaculite stones the shells just less dissolved and not as heavily cemented together.

Tried to make this point, failed.

Originally Posted by yuzuha

It would be pretty much like sharpening on a hunk of plate glass (you could always use ammonium fluoride to etch the surface to whatever degree of "frost" you want)

Also tried this point, apparently doesn't work that way. I suspected this was why the "solid" hones (jade, jasper etc, vs. "particle" hones-sedimentary/metamorphic from sedimentary- coticule, thuringen, japanese naturals, you know the ones every has used for hundreds of years) work- like a steel file: the texture provides the grit, rather than individually sized cutting particles- but I was told I was wrong and not given a reason.

Good thoughts though. You'll find that people are really iffy on the theory here and prefer experience. Even though the "uncommon" materials haven't really been tested enough to have any approximation at normalisation and to determine outliers.

From the responses so far, I apparently didn't explain myself correctly...

I have seen at least a dozen different threads from people asking how to fit Natural stones together into a progression for honing....I think it would be a wonderful thing to have a list to go from, and I also would like to know the same thing....BUT, instead of me asking lots of stupid questions that would be extremely hard to follow for the next person who wants to know the same thing, I thought having some type of comparison would be more helpful in the long run.

Originally Posted by khaos

....All that said I think it would be a great idea if instead of grits/micron ratings we made a chart of how the stones are best used in a progression. For example a Thury fits better towards the finishing end....

I am completely open to suggestions on how to put the chart together, but for the sake of starting the process rolling, I posted my idea first...I think this list is a doable thing, and I like your idea, how about maybe making say 6 categories?

Extra Coarse (Probably too coarse for Razors)
Coarse (The beginning stage for Razors)
Medium (Comparable to something like a King 1200)
Fine (Somewhere around the Norton 4000)
Very Fine (Maybe like the Norton 8000)
Polishing (Just for final finishing of the edge)

Does this sound like a more practical way to go at this? ...if not, make a suggestion!

Originally Posted by khaos

......Also, you completely forgot Japanese naturals.....

You are absolutely correct!

I know Bubkis about Japanese Naturals, but that is not to say I don't want to, just that if I don't get much help on this here, I'll probably pursue this on my own as I acquire more hones....But I have vowed to stay clear of the Japanese naturals until I have a complete set of the rest of the world's hones!

Too me that system sounds WAY simpler, easier, and far more practical. The bare bones of that are already in "what hone do I need" in the wiki, though it needs expansion.

EDIT:
In fact that would have saved me so much time in getting hones you don't even know lol....
(then there was the money factor too but...)