Thread: stone ID

I picked up a few rocks while walking in the nearby mountains with the intention of lapping them to see what I could see. Two turned out to be duds, but this one is much more interesting.

For starters, it's very, very hard. It's been harder to lap than anything else I have (C12k, barber's hone, etc.). As you might be able to see in the pic, there are no visible grains in the greenish areas - only tiny layer-like lines. The lack of grains is what originally caught my eye.

After getting it flat and smoothing out any edges that could catch a razor, I took an already-sharp razor and did a bunch of passes with a lot of water on the stone. Didn't seem to dull the edge. If anything, it felt sharper on my thumb pad. I noticed that the stone absorbs water fairly quickly, so I started just lightly misting the surface and honing until it was dry (probably 20 passes each time). Felt like it started to build a tiny bit of slurry as it dried.

Shaved with the test blade today and got the best shave I've ever had from that particular razor. One benchmark was that I was able to shave my upper lip against the grain with the spine completely flat on my face. The only other time I've been able to do that consistently is off of my Shapton 30k.

Anyway, I know it could be some kind of fluke, but I'm curious if anyone knows what kind of rock this is. Should I head back up the mountain with a pickup truck?

(click for larger pic)

Great find, but what are you still doing here? Go back and look for more

What is the size of the stone?

It's a big chunk of rock. With the right (diamond?) saw, one could probably get 4 or 5 hones out of it.

I really wanted to flatten one of its large faces, but after an hour or so with little progress, I settled for a smaller side that was almost perfectly flat to begin with. This lapped side is roughly 13cm x 6cm (5"x2.5")

Sure wish I could get the big face lapped. It ain't happening with sandpaper, though.

Adam,
Do you mean the side we are looking at came that way? It allready looks like it was cut intentionally and partially lapped.
Mike

Originally Posted by Kingfish

Adam,
Do you mean the side we are looking at came that way? It allready looks like it was cut intentionally and partially lapped.
Mike

This side I ended up using was very flat, but no, I don't think it had been cut before I found it and lapped it. It only looks that way now after several hours on about 3 meters of (now ruined) 80 grit sandpaper strip .

There was a razor hone of considerable repute that was found in the Arbuckle Mountains that was composed of indurated sandstone. The stone was indurated to a depth of 125 ft, but it was the stone on the surface that was the most prized, as weathering had erased the grain of the stone rendering it completely smooth. When you mentioned the lack of grain in your stone, this was the first thing that came to mind. Also, the porousity that you mention is typical of sandstones as well.
Alternatively, based soley on the colouring, it may be a modification of chloritic slate, various hones of this nature can be found all over the world.

Kindest regards,
Alex

Originally Posted by northpaw

This side I ended up using was very flat, but no, I don't think it had been cut before I found it and lapped it. It only looks that way now after several hours on about 3 meters of (now ruined) 80 grit sandpaper strip .

80 grit sandpaper doesn't work that well for lapping, I know because I wasted a lot of hours trying to lap a swaty with it. A coarse DMT or even a cheap diamant stone will work much better. Wet 120 waterproof sandpaper will also work better.

Interesting...

If the OP is willing to send me a private message
that has some location information I can take an afternoon
and try to see if there is a clue in the local geologic survey library.
I do not need exact info just a general vector from a
town or landmark.

To set expectations that area of the world is complex. It is
possible I could have more questions than answers.

The obvious question can you scratch it with a knife.
Can you scratch it with quartz.
Does it fizz when a drop of dilute acid is applied.

Is there a local university with maps or people that
might answer a question or two. You do not have to
ask about it being a 'hone' just ask about the rock
itself.

The interesting thing about that part of the
world is the complex mineralogy that the metamorphic
terrain generates.

Meta sedimentary rocks could very well produce great hones.
A very fine grained siltstone that was cooked just right
by mother nature could be excellent. If you are happy
to pick and choose you might get a pick-up truck of raw material
that is worth the effort even when a quarry operation would not be justified.

A mud or sand saw made of scrap could trim the blocks to size
trading time for diamonds.

Wow - great posts. It's kind of late, so I'll just make a short reply and be back with better pics and more information tomorrow.

At first, it didn't seem like I could scratch it with a pocket knife, but when I took the tip of an old chef's knife and leaned into it, it did indeed scratch the surface.

I'm going to try to hook up with Superfly here about it. I think he told me once that he knows somebody who's cut hones for him before.

Thanks for all the info!

Originally Posted by northpaw

.....

At first, it didn't seem like I could scratch it with a pocket knife, but when I took the tip of an old chef's knife and leaned into it, it did indeed scratch the surface.

I'm going to try to hook up with Superfly here about it. I think he told me once that he knows somebody who's cut hones for him before.

Thanks for all the info!

Seems to have promise. Get some blocks cut down
at least enough to try. save some chips for later....

I think you are showing the correct edge of the rock for use as a hone.
With an X pattern if the light and dark bits are not exactly the same
hardness it should even out and be consistent over time (as well as good
looking).

No mater what it is, if it hones well it is a hone.