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Cobaltocalcite pink to blue?


#1
Cobaltocalcite - Also referred to as "Pepto-Bismol" stone, due to
the real name being a bear. The pink color of the druzy is almost
exactly that of the medicine in the bottle. 

Noel, Actually, i think the “cobaltocalcite” is actually
cobaltodolomite. Calcite is CaCo3, dolomite is MgCo3. Whatever, the
coloration is due to a cobalt or cobalt-manganese impurity, which
would not be the same as cobalt carbonate. However, if you’ll tell me
the kiln tempaerature used to oxidize the cobalt carbonate to the
oxide, I’ll experiment with some pieces of the pink material and
pass the results on to the Orchid network. I bought a couple boxes
of it a few years ago in Tucson! My guess is that the dolomite will
just break down…

Wayne Emery


#2
Cobaltocalcite is presumably colored by cobalt. I know from decades
of ceramics that cobalt carbonate is pink, whereas cobalt oxide is
typical cobalt blue. Does that mean that heat or other treatment
would turn cobaltocalcite blue? 

Hi Noel!

I sure as heck wouldn’t know! That’s what my respected and trusted
gem dealers have told me it was when I bought it. They’re all
probably in Tucson (hating I’m not headed to Mecca, too), and too
busy to keep up with OrchidMail™. :slight_smile:

Anyhoo… cobalt… yes, I think blue. The only question I saw pop
up was cobaltodolomite being suggested by our respected friend Beth
Rosengard. The “cobalto” portion doesn’t seem to be in question…
but the rest???

Considering the relative abundance of Cobaltocalcite(dolomite) on
the market, and the other treated drusies, I suspect some marketeer
would have fried some of it to see what other “flavors” they could
create. I haven’t yet seen any such critters on the market…

All the best,

Dave

Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com


#3

Wayne, Actually, ceramic glazes with cobalt will come out blue
whether you start with oxide or carbonate, fire in oxidation or
reduction, at low temps or high (1500 to 2400 degrees F). I don’t
know what the minimum is, since ceramic clay bodies don’t mature (at
least, the ones I know about) any lower than that. What this
suggests to me is that cobalt “prefers” to be oxide given half an
excuse. For what it is worth, Mg can be used to produce purple
glazes, with some difficulty. It tends to do dark brown. So, if
turning the cobalt blue turned the Mg brown…yuck? And, dolomite
(also used in ceramics) is pretty soft stuff… I should leave
this whole area to the experts!if you’ll tell me the kiln
tempaerature used to oxidize the cobalt carbonate to the oxide, I’ll
experiment with some pieces of the pink material and pass the results
on to the Orchid network. I bought a couple boxes of it a few years
ago in Tucson! My guess is that the dolomite will just break down…


#4

Pick , pick, pick… The correct formulae for a carbonate is CO3 not
Co3. Co stands for Cobalt, C for Carbon O for Oxygen.

Tony