Thread: Natural Stones

Originally Posted by 111Nathaniel

I've heard of novaculite. Actually i thought i found garnets in that sandstone but they were K-seldspar crystals coated in oxydized iron...I wasn't thinking of slate because it is the metamophized shale but during metamorphism the crystals i'm looking for may form which never occured to me, so i'll take a look at the slate nearby. I did some research on the Belgium Coticule with my lab instructor, It was originally a mudstone that undergone particial metamophism becoming a "shist" causing the stone to grow microscopic garnets, in order for that to happen theres a very narrow margin of forces that must be present, thats why there's so little of it occuring naturally.

There are very few, if any, known Mn-garnet coticule deposits that suitable as whetstones outside of the Ardennes region. However, one deposit that probably comes closest is in the Port Felix area of Nova Scotia. I'm not able to upload the article here, but here's the reference: SCHILLER, E.A. & TAYLOR, F.C. (1965). Spessartine–quartz rocks (coticules) from Nova Scotia. Am. Mineral. 50, 1477-1481. You might also want to check into some of the folks doing work on NS garnets at Dalhousie University, Dept. of Earth Sciences. They should have a lot of info on the location of coticule-type rocks.

The (yellow) coticule where most of the garnet is found is actually volcanic material that was deposited on the mudstone and then metamorphosed. Hence, yellow (coti) over blue (BBW) in a natural combo.

Happy hunting....

Originally Posted by 111Nathaniel

Ok i see what you mean, yeah i have one sandstone that i rate at 700 grit. But it abrasive particles get warn quick and the binding is hard so i'm always refreshing it by rubbing it on cement. This is why i'm looking for Quartzite it's like a sandstone with mostly all quartz so it would be consistent and a fast cutter. yeah there would be few types of stone under 1000k and would be great stones, most are just ok.

Of course sandstone is quartz and quartzite is metamorphosed sandstone. Almost any rock has some qualities that make it useful as a honing medium depending on what you want to sharpen. It's a matter of many different qualities coming together in one rock that make it superior and that's why good honing stones are rare and expensive.

We have several Geologists on the forum here. My secondary major was Geology but that was eons ago.

Most of Canada is part of the Canadian Shield and the rocks are old, very old, mostly the basic kinds. Good luck in your hunt.

The picture below is Labradorite, basically plagioclase feldspar-type location labrador. NO not a honing stone.

Thanks woodash for you info, never knew about nova scotia's stones, I'll check into it. I brought my coti to the lab at the university we only based what i said about coti's on what we could visually see. We were actually wondering how such a difference in colour could naturally happen thanks for the info.

Yes what makes a good honing stone is an emergent property from so many different factors. thats a nice rock i'd love to go to Labrador but i can't help but try to figure out the background in the picture.

Originally Posted by 111Nathaniel

i can't help but try to figure out the background in the picture.

Appears to be Electric Light Orchestra.

I have some quartzite sawn into slabs. Haven't tried it yet as a hone.

Cool, perhaps you could tell how it turns out later.

I've seen this mentioned on the forum before, but you can find all kinds of stone already sawn into slabs on ebay and at "knap-ins" where like minded knappers congregate and swap and sell rock. Most of it is obsidian and therefore worthless as honing material, but if you go to a knap in you can look over some very interesting looking slabs.

I've tried several of my slabs on knives. The Kentucky hornstone, quartzite and a banded, unknown variety all will definitely cut steel with water and no slurry. they all remove steel rather slowly and really put a nice polish on my edges. Perhaps someday I will learn how to take those microscopic pictures so that I could show the edges.

Quartzite should be good, i have one that puts on a nice edge good enough to shave arm hairs. I think given that many hones people buy is or related to slate so i think i'm going to go to some areas where i know to be slate.

The age of needing natural hone stone is long past.
Thus the local quarries and pits will be mostly forgotten.

There are two keys -- mineralogy and grain size.
The grain size is the hard part and is best tested
with common steel and a look at the scratch pattern.
Compare with some known "standards".

A number of good hone stones are fired silt stone.
i.e. find a fine mud or silt stone and correctly fire it so it
is no longer mud when wet and you may have a winner.
Find a friendly potter... think terracotta more than
porcelain or stoneware.

In silt and mud stone the mineralogy can be
important but in some cases the shape of the fine
quartz grains can be very important.

As far as scratch test consider three bits of
steel. One soft and fully annealed, another
fully hardened (R62ish) and another tempered to
normal razor hardness.

If the mineralogy is not right it will make no
progress on hardened steel. A "finisher" need
not be hard and abrasive the way a bevel
setting hone must.

So hunt some steel to test with.
Common knives, cast off and broken razors, common
re-bar steel be inventive but purposeful and good things
will happen.