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Posted in response to agate versus jasper.... from Phil on June 16, 2004 at 14:38:27:

Re: agate versus jasper....

Hi Phil

Sounds like you are still trying to find an "easy fix" where there isn't one... - LOL :~}

As we discussed before, the basic difference between chalcedony and jasper is a structural one - at the microscopic level. It has nothing to do with the color or pattern. Chalcedony is composed of microscopic *fibers* of crystalline quartz. Jasper is composed of microscopic *grains* of crystalline quartz.

I'm not sure, but I think Jay may have offered a bit of light (sorry for the pun, Jay... :~} ) with his opaque vs. translucent info. It seems to me that chalcedony is almost always translucent, while jasper is almost always opaque - and I think it is the structural differences which give them these light transmission characteristics. Perhaps - and I'm speculating here - the quartz fibers in chalcedony act somewhat like the fibers in fiber optic bundles, transmitting light through them; while the grains in jasper act more like scatterers, the light bouncing back off them rather than being transmitted through. - Anyway, I think that if you can see light through at least parts of it, it's chalcedony - while if you can't, it's jasper. (Although I'm sure a thin enough piece of jasper - or the thin edges of larger pieces - might let a little light through...)

As for agate, it is a type of chalcedony - a "subvariety" - as is onyx.

Jay: Sorry, but I don't buy the "or other patterns" part of the agate definition you gave. That sounds like something that someone added to the definition of agate recently (past 30 or 40 years?) to account for the fact that the term has been so heavily mis-used over the years... In an after-the-fact sort of way it is correct - by default. :~} But like with the misuse of "sagenite", saying it's so doesn't necessarily make it so. - The classic definition of agate is chalcedony with concentric color bands; and for me that's what true agate is.



From Alan Plante - June 16, 2004 at 23:38:47
Email: alsher[ ]

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