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Sunburned turquoise?


#1

Good morning everybody,

Does anyone happen to know anything about “sunburned turquoise”?
Although I’m not sure now if that’s what the correct name was but it
was something akin to that. Basically it looks like howlite with
reddish-brown patches/areas. And darned if I can’t scare anything up
about it on the Internet!

Thanks so much, Carol

Part 2

After digging deeper, I think the “sunburned turquoise” about which
I submitted an earlier email is more than likely “Wild Horse
Magnesite”. I am still very interested to know more about it if
anyone can help enlighten me. Thanks again! Carol


#2

Sounds like a marketing gimmick to me. Exposure to direct sunlight
is not a problem with any Turquoise that I have mined, although I
have observed that some Turquoise which has been exposed over
millenia tends to be somewhat bleached. I have also observed that
Turquoise will turn brownish when burned with a torch. It is also
possible for Turquoise to be stained brownish by iron oxides which
have been exposed to the atmosphere for extended periods.( One
theory of the origin of Turquoise is that the copper that is
necessary to form it is derived from cuprous iron sulfides that have
been leached of their copper content by percolating phosphatic
solutions. Thus, the copper/iron sulfides that have been bereft of
their copper content become oxidised and the result is iron oxide (
a.k.a.rust ) which can permeate adjacent porous rock. The resultant
stain could, of course, cause the Turquoise to appear to be
brownish. Thuis kind of color alteration is common to the Royston
Mines in Nevada. Ron at Mills Gem, Los Osos, Ca.