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Turquoise identification

Stone Question… I have a ring, probably originally purchased by the
owner in the 30’s or 40’s. The stone is 3/4 inch x 1/2 inch, black
stone, with what looks like turquoise in two spots. The black part
is marked up, not smooth at all, the blue green part is smooth and
seems to be surrounded by the black.

What is this? Is it turquoise? If so what kind? what is the black
stone part? I’ve looked at pictures, seems more like Tibetan
Turquoise but the amount of black inthe ring and the amount of
Turquoise as far as surface area seems to be equal. I’ve never seen
a ring like this before.

Cautious to work on this piece, Ilene

Dear Ilene, The black portion of your piece may be the Palmetto shale
that is frequently the host rock for Turquoise occurences in Nevada.
There are a number of such mines where the Turquoise is such a minor
constituent that the resultant cut stones are of limited appeal. In
the Candelaria area there is an old mine that produced variscite
which occured as emerald green veinlets within the black shale.
Palmetto shale is aluminous and phosphatic thus it can provide the
necessary chemical soup that results in Turquoise or variscite. Ron
at Mills Gem, Los Osos, CA.

The black part could be matrix, dyed by shoe polish, a typical
treatment of that era. In any case, it is advisable to unmount the
stone before working on it. For identification, possibly either IJS
or Thunderbird Supply, both out of Gallup, NM might be able to help
you with the aid of at least a photo. They’ve both dealt in turquoise
for many years–longer than most of us have been alive–both going
into 3rd and 4th generations.

Dear Ilene, I can probably help you ID the stone but not with out at
least a really good photo. Sometimes the color of the turquoise can
help tell which mine the stone came from and sometimes the matrix
helps. Sometimes the combination of matrix and stone helps. If you
can send a color accurate photo please do to @Patania_s Sam

Irene,I have some pieces of Bisbee turquoise that I cut over thirty
years ago which have large areas of black matrix with small areas of
fine color turquoise such as you describe.Perhaps that is what you
have. I don’t know the composition of the matrix. Jerry in Kodiak

The black material is called the matrix. In many cases it is
slightly softer than the color part of the stone. If you plan on
re-polishing the stone you should take it out of the setting. One
caution: Some times the color portion of the stone will consist of
a vain running through the stone or it might be nothing more that a
round piece of gem material encapsulated in the matrix. If you pull
the stone out you may be able to determine how deep the color
material goes.

If the color material is like a round nugget re-cutting the stone
can produce two different result. The color portion could get
larger or smaller as you re-cut it. Think of shaving sections off
an orange. As you shave off more pieces the amount of the interior
of the orange will grow. Once you cut through the center of the
orange you will have the maximum amount of orange showing. Any more
slices will show less and less orange. The same holds true for a
nugget of gem material in matrix. Many turquoises have some form of a
matrix. The shape of the matrix and the color of the gem material
can help to identify where the stone came from and what type of
material it is. If you can, send a photograph to those who offered
to identify it. They have lots of experience and can possibly help
in identifying it.

Your Orchid Friend Lee Epperson

Irene, A lot of the turquoise coming from the Chinese and Tibetan
deposits have large areas of black matrix…this material is v= ery
common today and MUCH cheaper in the world markets than US material,
MUCH if not most of which has been, er, “stabili= zed”.

Wayne Emery

Dears: I=B4m just reviwing the last gems stones book I recived
(Pierres Precieuses by M. Fontana) from France, in this book you can
see a photo of a turquoise with a deep gray matrix of chalcopyrite.
Is a very special inclusion but it is posible, because the turquoise
is produced in the copper=B4s ore. Regards
Adriana in a stormy day in Santiago de Chile