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Ametrine mystery yet unsolved


#1

Wayne or anyone,

I’ve been collecting and reading up on ametrine for years, because
it’s a stone that to me, suggests an actual event. Apparently it has
yet to be determined why the crystals are purple on the free end and
yellow at the base. It sure keeps the imagination going. It’s pretty
much agreed upon that there was an “event” be it heat or radiation or
both and this makes perfect sense to me, especially since it’s mostly
localized to a region (in Bolivia). It all makes sense to suggest why
the color zone cuts across the crystal that is.

I’ve got numerous pieces of natural ametrine, rough and faceted,
cabbed and carved. I just love the stuff and haven’t set any of it
yet. All pieces have a linear demarcation, be it sharp or fading.
I’ve been seeing some pieces though on the web that have drifting or
curved demarcation and even swirled. Even pie shaped alternating
color zones. I always dismissed it until I read up on the Russian
process of crystal growth. I imagine they can start with any shape
seed and grow a citrine core, then finish it off in a purple jacket.
Their material has a very sharp line of demarcation. Lab stuff is
limited by the imagination. But then I saw on the Anahi mine website

http://www.ametrine.com/ametrine/

a mined specimen slice with the pie shaped color pattern! That sort
of blows my understanding of the flash wave of heat or radiation or
whatever it was that happened.

My question is this. “What the heck?” (for lack of better words) Does
it lie in the crystal growth pattern? Is this a slice of 6 fused
crystals that continued to grow after the suspected event and ended
up at varied heights? Or does this pattern undermine the theory of a
flash event?

There’s a story we just have to figure out, or really, wait until
someone does so we can read about it. Do you have any theories of
your own?

Jaye


#2

Jaye

The triangular zoning is understood to be a product of twinning
within what appears to be a single crystal of quartz. Different
valence (oxidation) states of the iron that are responsible for the
yellow of citrine and the purple of amethyst are caught up in the
two crystals that are twinned. But why twinned crystals growing
simultaneously in the same environment should have different colors
is pretty much a mystery.

Since the color zoning is determined by the crystal growth pattern,
straight lines are to be expected in natural material.

Incidentally, the change of oxidation state of the iron is what
causes some amethyst to turn into citrine when heated to the proper
temperature.

Dick Davies