Thread: BUBBLING GOTICULE

Originally Posted by khaos

I buy this explanation too. I still am in the camp that there may be some oil or soap in the mix somehow too though, because I simply can't think of a mineral that would make an elastic slurry, or even something that would increase the surface tension of water (let me remind you most things decrease surface tension...)

Well, who knows what was going on when this stone was forming. There could be trace amounts of organic material that, with water added, mimics the characteristics of soap. I think some salts have detergent properties as well. As for the surface tension, soap decreases surface tension. I think bubbles will form more easily when the water's surface tension is decreased. Of course, without a detailed analysis of this particular stone, we can speculate until the cows come home and never have a definitive answer.

It would be nice to know what is causing the bubbles and if that is what gives this stone it's outstanding polishing properties. If it is some salt or organic material, perhaps we could sprinkle it on other coticules (like fairy dust) to enhance the stones performance as a hone.

Originally Posted by radaddict

Well, who knows what was going on when this stone was forming. There could be trace amounts of organic material that, with water added, mimics the characteristics of soap. I think some salts have detergent properties as well. As for the surface tension, soap decreases surface tension. I think bubbles will form more easily when the water's surface tension is decreased. Of course, without a detailed analysis of this particular stone, we can speculate until the cows come home and never have a definitive answer.

It would be nice to know what is causing the bubbles and if that is what gives this stone it's outstanding polishing properties. If it is some salt or organic material, perhaps we could sprinkle it on other coticules (like fairy dust) to enhance the stones performance as a hone.

Nope, its a metamorphic rock subjected to heat and pressure. No organic material would survive it without being changed into graphite or some xtlized form of carbon.

Originally Posted by thebigspendur

Nope, its a metamorphic rock subjected to heat and pressure. No organic material would survive it without being changed into graphite or some xtlized form of carbon.

Ah well, it was mere speculation after all. So then, a metamorphic rock with perhaps metaphysic properties. The mythical hone of plenty!

There is an interesting article here about coticule formation and the elements in the sedimentary layers before they were transformed by pressure/stress/temperature into metamorphic layers.

The coticule in question (if indeed it is one - it certainly looks like one) would not be porous, except superficially at the surface and sides. It has been lapped, so any surface contamination should have been removed.

Three things that remain are (1) it isn't a coticule, (2) there is still contamination of some sort along the sides, (3) the water being used during honing.

I think I would try to rule out (2) and (3), for the former by lapping the sides and for the latter by using distilled or deionised water. Once those two have been taken out of the equation, only the rock is left. If the lapping has been thorough enough to rule out any user-induced contamination, then the bubbles must be caused by an inherent quality of the stone itself.

I don't know anything about specifics of how these stones were quarried, but I would like to know what layers would be found both above and below the coticule layers, and whether anything of the make up of these layers could be incorporated into the stone, in other words whether it came from upper or lower boundaries and contained something of another layer.

I have a BBW that has spots of yellow in it and which is a very fast cutting stone. BBW and yellow coticule hones come from the same area, so these two must be found in adjacent layers, and posibly my BBW was taken from the layer which shared a boundary with the yellow coticule layer, and incorporates part of that layer within itself. Perhaps some other contiguous layers have added something to this foaming coticule?

Not being a chemist or geologist doesn't help, but I have seen the word "montmorillonitic" mentioned in connection with the upper layers of coticule strata, and that some forms of this material are called saponite, or "soap-stone" - but whether this is found in the Ardennes I don't know, or even if it is found in close proximity to metamorphic rocks like coticule.

Regards,
Neil.

After keeping this stone 4 hours in distilled water and lapping 45 minutes until 1k i did test it again.
At first i have to say bubbles comes way less then it was before. if slurry is consentrated more bubbles smaller and vs verse.
This make me think Owner of this stone used soap for a long time that is why they are coming out. ( this is just opinion.) i start to test it is quality it still does exact work before. i should say wonderful edge . i haven't shave test it but i will test it later.
Below more picutres after washing and lapping . I made couple picture to compare my another coticules Natural combo and another one seems like wood root.enjoy.

The lather/soap-theory doesn't convince me: soap and lather dry far to quickly to penetrate any significant depth into the stone. And as it is very soluble in water, the effect wouldn't be very long lasting - especially after repeated lapping, rinsing and soaking. Also: detergent would have bubble-generating properties with and without slurry.

Especially after seeing these latest pics, I think it's oil residue. It is a largish stone, as used by carpenters. They often used coticules, especially the harder ones, with oil. This changes the colour to a particular type of bland hue with light (even greyish) and dark blemishes, especially when dry, at the same time lending it a more 'transparent' (butterscotch texture like) aspect.

Oil would eventually penetrate a coticule, and can't easily be gotten out. A mixture of oil residue and very fine (because hard) coticule powder could produce a bubbling mixture with water. It would explain the difference with and without slurry.

I've got a large carpenters' coticule that was used with oil too. I don't usually use it with slurry, but will try and see if I can get to make it to bubble.

I can verify that come substances are capable of penetrating a Coticule.
I had this hone, made from a piece of raw Coticule, that I had picked up at an old abandoned mine.
The slab of stone I managed to cut out of the rock, turned out with a small cavity. I filled the void with a paste I made from candle wax and Coticule powder. I heated the stone till the molten pasted started to flow into the void.
To my surprise also the surrounding area absorbed part of the wax. I lapped a good part of the hone, but the slight discoloration stayed visible. There was no disadvantage for honing. The stone performed as good as before (I only filled the void for cosmetic purposes) and I don't recall any foaming (wax isn't oil of course).

Here's a picture:

You can clearly see where the wax soaked into the hone.
As far as Neil Millers excellent post goes:

As far as I know, Coticule layers are all sandwiched between Blue schist. Some of that schist contains enough spessartine garnets to have honing qualities of its own. (Belgian Blue whetstone).

Here's a list of the mineralogical components of Coticules:
Spessartine (the actual garnets)
Muscovite
Paragonite
Quartz
Chlorite Mg (a greenish mineral)
Hematite (little in Coticule, a lot in BBW)
Apatite
Rutile (titanium dioxide, a very common pigment in white paint)
Koalinite (also common in paint and as filler in paper production)
Andalousite

I lack the knowledge to really tell if some of those would form a suspension with water that easily foams. Titanium dioxide and Kaolinite seem the most likely candidates in that field. Kaolinite (2 Mohs) is one of the softest elements found in Coticules. We are talking about a very soft stone that forms slurry from merely rubbing a razor over it. So we should probably look at those elements in the first place.
Chlorite (2.5 Mohs) is very soft as well, but in high concentration it would add a typical green hue to the hone.

Beware that I am talking about "Coticule" rock as it is found in the Venn Stavelot massive in Belgium. Coticule formation in the geological sense is a very interesting phenomenon and well studied all around the world. Not all Coticule formations have the same mineralogical composition so we have to be careful with quoting literature about other finding spots of Coticule (with too impure or narrow veins for honing purposes).

Best regards,
Bart.

Originally Posted by Oldengaerde

I've got a large carpenters' coticule that was used with oil too. I don't usually use it with slurry, but will try and see if I can get to make it to bubble.

The results of this test do not corroborate my theory; though I could produce small bubbles with the fatty slurry mixture, none were formed during honing.