Stone identification / Arkansas (Hard, Surgical Black)

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Papilio

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Sep 6, 2019
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Hi guys,

I know that natural stones have disadvantages. But my experiences have been positive until now.
I need advice concerning Arkansas Stones.
1. A Hard Arkansas is mostly pure white. Mine has a larger brown spot that goes through the hole stone. Ok or lack of quality? A pocket stone I own is pure white.
2. Could this be a Surgical Black? It looks so pale. From what I know Surgical Blacks are darker, black or blue-black. But it is tagged, welded and the manufacturer is well known.
The Hard Black is darker than the Surgical Black? I know that natural stones are not always the same and can vary in colour. But the Hard Black is rathere grey than black and should be paler. The Hard Black looks familiar; I already have some pocket stones and the pocket stone has the same colour. But every video and photo I have seen shows a Surgical Black being darker, (nearly) black.

Some photos following:
1) Surgical Black next to Hard Black
2) Surgical Black
3) Hard (brown spots).

1) Surgical Black vs Hard Black





2) Surgical Black





3) Hard Arkansas






Neither the manufacturer nor the retailer answer my contacting.
I am grateful for any helpful hints.
 
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RH Preyda is what became of Halls' Arkansas Stones (hence the RH). The Halls were great folk with excellent products. They sold and retired.

I've never had a good feeling about the new organization.

Comments like this from their site are part of why...

Prized by craftsmen worldwide, RH Preyda Bench Stone is the only known substance that can sharpen a blade and polish it as well.

They may be great to deal with but I look elsewhere these days.
 
Ok, sad to hear. I read posts from guys who mentioned that their stones are always good qualitiy.
The important thing: Can this pale-grey stone really be a Surgical Black? That's what's really making me mad.
 
Again, they may be great, I just choose not to go with them.

Like you said, colors can be misleading, and I'm surely no novaculite expert, so it's hard to say. As I'm sure you've learned they technically gauge them by density.
 
Eli Chaps said:
Like you said, colors can be misleading, and I'm surely no novaculite expert, so it's hard to say. As I'm sure you've learned they technically gauge them by density.
Click to expand...

That's a good point. I know that they are gauged by densitiy (Soft, Hard, Hard Black, Surgical Black, Translucent). As I said before: Watching sharpening videos on Youtube Surgical Blacks always look "pitch black". As they do on photos (online shops).
Maybe there are a few guys that own Arks and can tell first hand what their stones look like.
 
I own and have owned several. My experience is soft and hard can have a lot of color variation. All my surgical blacks were very black.
 
As far as I know Arkansas stone grades are entirely arbitrary, meaning a distributor could legally call it anything they want. However in every case that I have seen "black" means black. The white-with-brown stone you show could be a true Hard White by commonly used naming I think, as color variations seem to be acceptable, with density being more important. Look at Dan's Whetstone, Best Sharpening Stones, and Natural Whetstone Company for some other grading examples.
 
Lots of places have used surgical for differing shades of stone. I wouldn't worry about it too much. For me at least, "hard black" is usually the blackest stone. Surgical black is the "translucent" black stone, which often looks gray. It isn't really a big deal either way on what the coloration of the stone is. The density is the important part. Put a flashlight on your gray stone right on the edge of the stone in a room with the lights out and see if it transmits any light through the stone near the edges. If so, it's probably a good stone.

There will be next to no difference between a good dense pitch black stone and a good dense "translucent" black stone, so don't worry about the color too much. An Ark is something on the order of 99.9x% silica, so if the stone approaches the density of pure silica (2.65g/cm³) it's very dense, with little in the way of porosity.
 
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Yes, as said grades of stone can have different color variations. It might be the same color throughout or a mix.
You want something heavy for it's volume - the heavier the finer.
 
Papilio, grades of Arkansas stones are based on density/ specific gravity. Thus, weight is involved. Hall's has been good. Dan's Whetstones
are good as well and has good information on their site. I've seen the grey stone called 'surgical black'. The jet black is more rare as they have been mined out. It is the finest.
Then translucent, hard, white= soft, then washita the most coarse of these stones. These work for simple stainless & carbon steels. The black
will give a good shaving edge on a straight razor and double edge blades. DM
 
David Martin David Martin Best Sharpening Stones testing showed Translucent as finer than Black. I know Dan's lists it the other way, but since Best provided their results I used that for my chart. Do you know of other test data for these?
 
Thanks for all your replies.
Not only Best Sharpening Stones rate Translucent finer than Surgical Black (True Hard Black / Dan's Whetstone Company?).
Surgical is 4.000-6.000 JIS, Translucent 8.000-10.000.

Back to the densitiy. I put the stones on the scales.
Soft: 227,5g
Hard: 240g
Hard Black: 250g
Surgical Black: 268,5g.
Does this have any relevance? Could this be a hint that the heaviest stone is indeed a Surgical Black because it is heavier than the Hard Black?

The trick with the flashlight didn't work. I couldn't see any light shining through the edges.
 
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If all the dimensions are the same, then yes, heavier should mean denser and denser means finer.
 
If the stones are the exact same dimensions then yes, that would indicate that the gray surgical black stone is the most dense of your set. The "real" rating by manufacturers is specific gravity but that is just comparing the stone's density to the density of water, which at room temperature is as near to 1g/cm³ as to make no difference. The terms are effectively interchangeable in this case.

Black stones are not "mined out" - this is a common misunderstanding. There are still many many thousands of tons of novaculite available to be mined. Of all colors. The deposits are vast. Some are just not economically or easily reachable.

These stones are natural objects. At some mines, black stones may be denser than the translucent. Others it may be the opposite. Some stones may be bonded together tighter than others also, which makes them act finer.
 
Yes, the dimensions are the same.

The dimensions are: 152.4 x 50,8 x 12.7 mm.

Density (g/cm^3):
Soft: 2,31
Hard: 2,44
Hard Black: 2,54
Surgical Black: 2,73.

I have read somewhere that the density of Arkansas Stones is between 2.25g/cm^3 and 2.5g/cm^3.

What would mean that I didn't do the math correctly...Anyway, it makes some sense. They become heavier and therefore denser the finer they are tagged.

Well, I thought (and still think) about returning the Surgical Black. But after all your answers maybe I keep it.
 
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Mr.Wizard, sure. Dan's lists the black as finer. In the website: 'Sharpening Made Easy' Mr. Bottorff has a chart & lists the black at 1000 grit-- 9 micron. I have tuned my razor on both the black and translucent. Then shaved,-- as far as the shave goes both give a nice close, smooth shave. My black 'feels finer' but I'll admit my black is more broke in.? So, it may depend on what site you look at. DM
 
When Dan's Whetstones says that their black stones are finer than translucent, they mean the stones from their mines specifically.
Because a grade of stone can have color variation, it's also true that there is density variation within a color.
For instance, I've found that Norton's translucent cuts coarser than Dan's Black or Translucent. Dan's Translucent is coarser than his black, but not by much. Really if you have one, there is no reason for the other stone from Dan.
Also Dan's finishes his stones better for fine finishes. A lot of people have wished his coarse stones were finishes coarser.
These stones also wear in, so that black stone will become finer with use. The reason I haven't upgraded to a larger hard black is that I'd be giving up the wear I've put into the one I'm using.

So you have issues with proper grading, differences in veins, the finishing on stones, and (if you are buying used) wear on top of color variation.
 
Yes, Dan's finish is good on these stones. The grade I use most among these is the Washita at 500 grit. My black Arkansas is a Norton and is Jet black. It is very hard and fine. My translucent is also a Norton stone. My washita is from a roadside vendor in Hot Springs, AR.. I had to level and finish it but it has been a good one. I have 2 of this grade and one is a 4"X 8" stone. A nice size to work on. I wish I had other stones
that size. Good luck, DM
 
To be black or not to be black. That is the question. ;)
All those stones look quite ok. No chips. Seem to be flat. The Soft feels rather rough, but will probably get finer when used. The Hard Arkansas feels smooth. The other two are still wrapped.
Well, I think I will try my luck.
Hope I won't have to regret that I decided to by those Arkansas Stones.
 
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