name that stone

["anthony_marbella Last Name" <anthony_marbella@xxxxxxxxxxx>]

I want to begin by saying how much I love this list. I
get so much out of the internet, pertaining to the
subject that I am most passionate about, by belonging to
this group. With that said I also want to say that it
seems like that discussions have slowed down a little
bit, maybe everyone has been busy carving away.

Now, back to the subject. I am still unsure what kind of
stone I am carving right now but I have some new info on
it.  I have been carving with a 4-1/2 diamond blade on
my electric Milwaukee Angle grinder. I was amazed with
the ease that the blade could cut this seemingly hard
stone. This stone immediately kills the point on my
chisels and the only mark I can make on it with my most
trusty files and rasps is the residue left behind as the
stone removes metal from them. I like my tools so I
quickly gave up using them and am now having great
success with my grinder. I took a nice size chip, that
had been cut away with the grinder, and proceeded to do
a little polishing test to see how the stone would
react. What I found was that using wet  300 grit
automotive sandpaper, I was able to achieve a glassy /
clear surface (when wet) in a short amount of time. I am
sure that it will take an extremely high polish if I go
through my usual progression of sandpaper and buffing
compounds.

I tried the vinegar test and there didn't seem to be any
kind of reaction, so I guess that rules out the chance
that it is calcite.

I also tried to take a good look at the crystals and
fracture angles and, I'm not sure, but I think I noticed
some fracturing at right angles. It also seems like, at
certain points where stress or water caused fissures on
the surface, the stone breaks away like a layer that
wraps around the inside of the stone - kind of how the
earth's crust wraps around the mantle then the core.

I'm not sure if this is just an isolated characteristic
due to sections of the stone that have been subjected to
the environment or if this is a property of the make-up
of the stone.

I also wanted to point out that I was able to flake off
tiny bits with my fingernail that looked loose due to
the cuts of my grinder and then I could take them and
break them into extremely small grains between my
fingernails. These grains seemed kind of squarish but
were so small that they could have been round.

That is all I have for now, but I'll right more if I
notice any other findings.

Thanks,
Anthony Marbella - Sculptor
Pittsburgh, Pa