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'True' hybrid layer - what vein?

yohannrjm

Well-Known Member
There's been some discussion on these boards about whether the hybrid side on the Les Latneuses is really a true hybrid (read: mixture of yellow coticule and BBW) after all. In some stones it certainly appears to be very hard.

One thing I've noticed is that in natural combos the interface between the yellow coticule and BBW layers is usually very sharp (though there are sometimes streaks of blue in the yellow layer). As in this stone, for example:

IMG_2446.png


(Don't worry about the dishing on the coticule layer on that stone, I only use the BBW on that one anymore.)

Now I've got a slurry stone from an unknown layer that seems to have a gradual increase in 'pinkness' at the interface between the coticule and BBW layers. Note the fuzzy interface between the layers in the pics.

I was wondering if that pink layer would be a more ideal 'hybrid' layer. It does seem to have a mixture of BBW and yellow coticule. I've seen coticules with pinkish tinges, so could those be coti/BBW mixes?

Also, does anyone have an idea what vein this slurry stone is from?

NOTE: The pics do not show the true 'pinkness' of the interface between the coticule and BBW layers. It's actually quite pink, with speckles of yellow mingled in. It was hard to capture, and it doesn't show up well here.

IMG_2769.png


IMG_2767.png


IMG_2768.png


I'm looking forward to hearing your views on this.
 
That is a very typical La Grise, the upside, actually. To understand why I say "upside", we have to consider the geological formation of Coticule. The Blue rock originates from massive sedimentation of clay-minerals on the bottom of a sea more than 400 million years ago. This was a very slow process that took place over long time periods. The yellow Coticule layers, originate from ashes that sank to the bottom after massive eruptions from a nearby volcano. This was relatively a faster process. Because the concentration of ashes were largest in the beginning, most Coticule layers start of abruptly on top of the Blue rock. But after the Volcano stopped pumping ashes in the atmosphere, the sedimentation of the ashes slowly diminished, and got intermixed with the blue sediment. For this reason, the transition back to Blue is a more gradual one.

Here's the top junction of a La Veinette:
[img=800]http://www.coticule.be/tl_files/Coticule%20Vault/Coticule026.jpg[/img]

And the bottom junction of that same layer:
Coticule010.jpg


They way they're cut, you'll mostly see the same junctions at similar layers, because often one junction is weaker than the other, or it's straighter, which is another reason to favor it when cutting Coticules. Sometimes theres only Blue on one side of the Coticule part and "gres" on the other.

It is correct that hybrid side is not a very well chosen term form the inner side of Les Latneuses. I write "inner" because that part of the rock is sandwiched in between 2 distinct Coticule parts. The whole is called Les Latneuses, but you can actually have the "inner part" + "bottom" or the "inner part" + "top". I've already seen one as "bottom" + "inner part" + thin layer of "top". I don't know what the composition of the "inner part" is, but it's not entirely the same as a blue mixed with yellow, as I originally thought, and based the name "hybrid" upon.

Kind regards,
Bart.
 
Bart said:
That is a very typical La Grise, the upside, actually. To understand why I say "upside", we have to consider the geological formation of Coticule. The Blue rock originates from massive sedimentation of clay-minerals on the bottom of a sea more than 400 million years ago. This was a very slow process that took place over long time periods. The yellow Coticule layers, originate from ashes that sank to the bottom after massive eruptions from a nearby volcano. This was relatively a faster process. Because the concentration of ashes were largest in the beginning, most Coticule layers start of abruptly on top of the Blue rock. But after the Volcano stopped pumping ashes in the atmosphere, the sedimentation of the ashes slowly diminished, and got intermixed with the blue sediment. For this reason, the transition back to Blue is a more gradual one.

Interesting, so the bottom side of a La Grise combo will not have such a gradual transition?

Bart said:
It is correct that hybrid side is not a very well chosen term form the inner side of Les Latneuses. I write "inner" because that part of the rock is sandwiched in between 2 distinct Coticule parts. The whole is called Les Latneuses, but you can actually have the "inner part" + "bottom" or the "inner part" + "top". I've already seen one as "bottom" + "inner part" + thin layer of "top". I don't know what the composition of the "inner part" is, but it's not entirely the same as a blue mixed with yellow, as I originally thought, and based the name "hybrid" upon.

I remember that Yohann's hybrid-only coticule (the one he received from you, Bart) had a quartz "inclusion" on one end, which reminded me of novaculite. The hybrid side of my Les Latneuses also reminds me of novaculite, having a similar feel and hardness. Yet, the surface texture of it doesn't seem to matter as much as it does for novaculite. I should rub the hybrid side of my Les Latneuses slurry stone against one of my translucent Arkansas stones and see which wears first. My theory is that the hybrid layer is actually quartz-rich coticule (or coticule-rich quartz, depending on how you look at it). Well, that's been my theory for a while, but no one has commented on it before. :p
 
Could be correct. I don't know. Microscopically, at 80X, I can't see much differences between a "hybrid" side of a Les Latneuses or any other Coticule. Without some kind of mineralogical analysis, we'll never know.

Kind regards,
Bart.
 
That's a very clear explanation for the sharpness/blurriness of the coticule/BBW interfaces, Bart. Thanks a lot.

I wonder if the mixed coticule/BBW region has any interesting honing properties. I've never had a true hone with that mixed layer, and I'm sure people would prefer to have a thicker 'pure coticule' layer, so it may take some time to wear down a hone to that region anyway.
 
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