Weird and wonderful new combo coticule

I recently received a new coticule from The Superior Shave. I explained to Jarrod what I was looking for and he made a recommendation. I wanted a 40 x 175 mm stone to see if narrower would be easier, and I wanted something a bit different in feel than the stone I already had. Jarrod made a recommendation and I ordered that stone. When he was getting it ready to ship he emailed me to tell me it turned out that stone was a natural combo with bits of pink on the blue side. I hadn’t been looking for a combo as I have a 50 x 150 BBW but thought it would be interesting to see what it was about. This is the stone I received:

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It has an interesting look on both sides. The yellow side has what looks like stretch marks on the belly of a woman who has recently given birth. For those of you who can’t relate to that I’ll say it has lenticular striations at an angle and the cells have round inclusions in them. The overall effect is iridescence, with a sort of pearly depth to the stone surface as if tiny grains are floating in a liquid. The blue side is similar with the inclusion of a couple of pink dots on it.

The stone has a strange sort of feel to it. With slurry on either side it has a subtle sandy feedback but the most noticeable thing is a gummy sort of resistance to the blade sliding along it. This gets stronger as the edge gets sharper and toward the end of the slurry dilution hollow blades emit a whistling squeak. On plain water the gummy resistance is very strong on some blades, actually inhibiting a light touch and being a bit of a pain. Rinsing every 10 laps or so when doing X strokes on water alone reduces, but does not eliminate, the sticky feeling, which gets worse and worse as sharpening proceeds. I tried putting some shaving lather on the stone, which eliminates most of the sticking, but also most of the feedback. Lately I’ve been dipping the stone in a sink of dishwater, since I’ve been honing at the kitchen sink (ah the advantages of not being married). A solution of dishwater lubricates the surface and eliminates most of the gummy sticking, and the garnets that wash off get the dishes nice and clean afterwards ☺

The sticking was an annoyance and hindered a nice, gentle delicate dilucot procedure, as I’d have to push too hard to overcome the stickiness. I was reading on Bart’s site and somewhere he said that the blue stone on slurry can create a sharper edge than the yellow on slurry. I had been reading about combining the blue and yellow stones starting with the yellow on slurry, proceeding through a blue step and finishing on the yellow. So I played around with that and last night ended up with some pretty sharp razors using a method I outline here. They weren’t the sharpest, only popping hairs every once in a while, but I could go from dull edge to ready for the strop in 5 minutes or so and it minimized the time on the gummy, squeaky stage.

Drag edge at about a 45-60 degree angle across side of hone on both sides of blade to dull and clean up edge. Do this one or more times until it feels right.
Build thick slurry on blue side.
Set of 20 half strokes on each side of blade, (add gentle circular motion on warped edges with problems)
Repeat set of 10-20 half strokes until entire edge gets the “feel” The feel is that feeling that nothing is changing as you stroke suggesting the rock has done what it can at that level of slurry. On this stone on both sides the feel is usually accompanied by a rapid onset of the gummy feeling and whistling on a hollow ground blade.
Wash half of stone off under running water
Repeat sets of 10-15 half strokes until the “feel”
Wash half of stone off under running water, etc.
Repeat 4-6 times until the stone is pretty clean of slurry
By this time the stone is grabbing and squeaking after only a few strokes
Rinse stone and blade well with rubbing of fingers
Repeat a set of 6-15 half strokes on just water (edge matures faster now so fewer strokes are required to get the feel)
Rinse well, do set of 10-15 X strokes on blue, harder to do more because of building gummy resistance, dishwater helps keep it light

At this stage the edge shaves arm hair better than any other edge I’ve ever created. Mouth dropping good, I did a double take first time. 50 licks on my leather strop and it will vibrate on the HHT and occasionally pop the hair. On one blade it popped hairs off the stone with no stropping.

At first I was finishing with 20-50 X strokes on the yellow side with only water. But I noticed that the arm hair test seemed worse after that treatment. Those blades would pop hairs on the HHT erratically, but I shaved with them this morning and had nice, smooth shaves with no irritation. Maybe not the sharpest but good shaves.

Today I played with omitting the final yellow lap and the edge seemed at least as sharp. Tomorrow I am going to try shaving with the blade that came off the blue side and was stropped without honing on the yellow side.

So this is a strange and wonderful stone. Has anyone else experienced the stickiness? It really feels like there is a gummy substance on the stone, but it is clean as a whistle. I relapped it thinking maybe it wasn’t quite flat but it was and the lapping didn’t change anything. The sticking gets worse and worse as sharpening proceeds, and is worse on some blades than on others. I’ve read of a suction developing between the blade and stone and it feels kind of like that, but with that weird gummy vibe. I pretty much can’t hone just on water without a surfactant of some kind, dilute dishwater being pretty good. Does anyone else need a lubricant to hone on a coti? Bart talks a bit about honing with lather on his site.

This stone is awesome even with (or is it because) of that trait and I love the longer, narrower stone for honing. The blue side is very interesting, more so than I anticipated. I had never really gotten the point of a combo before. Having a combo means you are setting one of the sides down on a surface that in my kitchen may have crud on it, so I have to be more careful. I had a separate blue and having two stones seemed more practical than two in one. But the blue side on this is totally different than my other blue stone and from what I’ve read it seems to have something to do with the juxtaposition of the layers and migration of minerals before or during the metamorphosis.

Any feedback would be appreciated as well as anyone’s educated guess as to what sort of layer this particular combo came from.

That is one interesting stone. Nice acquisition. The reddish striations are reminiscent of the pink/red coticule I picked up from Jarrod, which also squeaks at times and feels a bit sticky. I am afraid I cannot tell you the layer, only that the stone I have cuts quickly and well, is fun to us, and quite different from my other coticules.

Good luck with the new stone.

Here is a picture of the surface of my red stone at about 200x and another of the red stone and another smaller yellow with green tinges.

Do you know the grits of the stones?

natchez said:

That is one interesting stone. Nice acquisition. The reddish striations are reminiscent of the pink/red coticule I picked up from Jarrod, which also squeaks at times and feels a bit sticky. I am afraid I cannot tell you the layer, only that the stone I have cuts quickly and well, is fun to us, and quite different from my other coticules.

Good luck with the new stone.

Here is a picture of the surface of my red stone at about 200x and another of the red stone and another smaller yellow with green tinges.

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I will agree that it is an interesting stone and a nice acquisition! I have a La Grise stone (identified by Bart) that is very very sticky in use and has a bit of red in it, but I will say it's not fast at all, and my slowest Coticule (in comparison to my La Petite Blanche and Les Latneuses.)

I will also say that what's most important was being able to shave with a smooth and comfortable edge! There's nothing more satisfying, and whatever stones/methods we use to get there, if the result is there that is all that matters! Congratulations, and that is indeed a beautiful stone!

natchez said:

That is one interesting stone. Nice acquisition. The reddish striations are reminiscent of the pink/red coticule I picked up from Jarrod, which also squeaks at times and feels a bit sticky. I am afraid I cannot tell you the layer, only that the stone I have cuts quickly and well, is fun to us, and quite different from my other coticules.

Good luck with the new stone.

Here is a picture of the surface of my red stone at about 200x and another of the red stone and another smaller yellow with green tinges.

Click to expand...

Those striations are reddish? Ok, I'm slightly red green colorblind so it has to be pretty red for me to notice. The lines do look like your yellow stone and the pink stone is the color of the dots on the blue side. Wish Bart would build a dichotomous key to coticules. Ultimately it doesn't matter of course, what layer it comes from, only how it hones, but it is interesting in that nerdy sort of geological OCD way we have about us.

Luc, I wouldn't have a clue what grit it is having no stones of defined grit above my 1200 diamond plate. The edges under the scope are just lovely at 300 power, my highest on the dissecting scope I have. No micro chips, minimum wavey edge, no burs at that power. Just lovely. I had a problem with chipping on my other stone but whether I'm just getting better at this, or this stone is smoother or maybe just that I can control the pressure and angle better with the narrower stone I'm having much better success with this one despite the grabby texture.

Brownbear said:

Those striations are reddish? Ok, I'm slightly red green colorblind so it has to be pretty red for me to notice. The lines do look like your yellow stone and the pink stone is the color of the dots on the blue side. Wish Bart would build a dichotomous key to coticules. Ultimately it doesn't matter of course, what layer it comes from, only how it hones, but it is interesting in that nerdy sort of geological OCD way we have about us.

Luc, I wouldn't have a clue what grit it is having no stones of defined grit above my 1200 diamond plate. The edges under the scope are just lovely at 300 power, my highest on the dissecting scope I have. No micro chips, minimum wavey edge, no burs at that power. Just lovely. I had a problem with chipping on my other stone but whether I'm just getting better at this, or this stone is smoother or maybe just that I can control the pressure and angle better with the narrower stone I'm having much better success with this one despite the grabby texture.

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The grit seems very low looking at the pictures but then, it doesn't mean much...

The most plausible candidates for the red streaks are i) hematite (Fe2O3), or ii) very finely-divided garnets (seems unlikely). Hematite is a common constituent of the BBWs, but not so much in the coticules, so there could have been some influence from one alternating layer to another as these rocks were altered/compressed. Grit is, to me, somewhat of a feckless concept in coticules. There are really many other factors contributing to how these things work in addition to garnet size alone.

Beautiful coticule, btw.

Woodash said:

The most plausible candidates for the red streaks are i) hematite (Fe2O3), or ii) very finely-divided garnets (seems unlikely). Hematite is a common constituent of the BBWs, but not so much in the coticules, so there could have been some influence from one alternating layer to another as these rocks were altered/compressed. Grit is, to me, somewhat of a feckless concept in coticules. There are really many other factors contributing to how these things work in addition to garnet size alone.

Beautiful coticule, btw.

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The hematite might contribute to the speed. This stone looks coarse under magnification but the surface is very smooth, no different than my other stone. Feels the same to my tooth. Those little seed like inclusions in the close up look really rough, but they although they are clearly different than the surrounding matrix they don't protrude and seem to wear at the same rate. A lot going on in this little stone.

Shaved off the blue only blade this morning. It worked but I had some pulling, so I clearly need to put it on the yellow side to finish. I'm going to try some different soaps to lubricate the yellow for the final finish. Probably will try shaving lather again, it really slows the stone down but might make a good finishing combination.

Brownbear said:

Those little seed like inclusions in the close up look really rough, but they although they are clearly different than the surrounding matrix they don't protrude and seem to wear at the same rate.

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Possibly these are some coarse garnets.

I've had stones with those grains in them before. Those are definitely not garnets. MUCH softer than steel.

SliceOfLife said:

I've had stones with those grains in them before. Those are definitely not garnets. MUCH softer than steel.

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Ulrich Kramm, in "The Coticule Rocks Spessartine Quartzites of the Venn-Stavelot Massif,
Ardennes, a Volcanoclastic Metasediment?" writes the following

Ulrich_Kramm said:

Kaolinite is present in some of the coticules of types 1, 2, and 3, where it prefers the spessartine-rich marginal parts. Frequently, it forms spots of 0.1-1 mm diameter, which are rich in inclusions of rutile, garnet, and quartz. Andalusite is observed rarely within these spots (Theunissen, 1971; Kramm, 1973)

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I am not a mineralogist, so I have no way of knowing if these spots qualify to be Kaolinite (Steve probably can tell us that).
But the reported size of the spots seems about right. I have often seen them in the surface of Coticules, and can confirm Ian's observation that they appear to be quite soft. Kaolinite, by the way, has a Mohs hardness of 2 -2.5.

It's a beautiful stone. Most La Dressante Layer, or La Grise, being the most likely candidates for a layer determination.

Kind regards,
Bart.

Bart said:

Ulrich Kramm, in "The Coticule Rocks Spessartine Quartzites of the Venn-Stavelot Massif,
Ardennes, a Volcanoclastic Metasediment?" writes the following
[snip]
I am not a mineralogist, so I have no way of knowing if these posts qualify to be Kaolinite (Steve probably can tell us that).
But the reported size of the spots seems about right. I have often seen them in the surface of Coticules, and can confirm Ian's observation that they appear to be quite soft. Kaolinite, by the way, has a Mohs hardness of 2 -2.5.

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Unfortunately, without analysis Bart (or at least looking at the stone), I can't tell. It possibly be kaolinite, but my guess is that kaolinite is unlikely. In the coticules that I've seen, kaolinite is a very minor/trace component (much more in BBW), and much more finely-divided. Kaolinite is also platy and tends not to form nodules or be ~equidimensional. Additionally, I don't really agree with Kramm's statement that ['kaolinite] forms rich in inclusions of rutile, garnet, and quartz'. That's just not very likely, IMO. But again, all this is speculation without a first-hand look.