TYPES
OF MEXICAN OPALS
Only about ten percent
of Mexican water and fire
opals are fashioned as
cabochons. The remaining
opals exhibit little to
no play-of-color, and
are faceted instead. There
is also cantera, sometimes
called "Mexican boulder
opal, "a unique and
interesting material that
is cut with the mother
rock intact. Some black
opals are mined in Mexico,
though very rarely. |
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Weight
: 3.66 ct
Size (mm): L 13.8
x W 10.3 x
D
5.95
Untreated
US $500
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Faceted
Fire Opal
Faceted fire opals may
have a body color of red,
orange, or yellow. Red
to orange stones occur
in a wide range of tones,
from levels 7 to 3. Tones
7 and 6 are red, while
levels 5, 4, and 3 appear
orange. Yellows are light
in tone, and more suited
for the mineral collector
than for jewelry. The
photograph shows an orange
fire opal with a tone
level of 4. |
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Faceted
Fire Opal
Most fire opals that exhibit
the play-of-color effect have
an orange body color, as shown
in the quality scale on the
next page. Very few red fire
opals exhibit play-of-color,
but some will show the effect,
such as the opal pictured here.
The production of bluish water
opals is estimated to be less
than half that of the orange-colored
fire opals. |
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Weight : 1.65
ct
Size (mm): L 9.3 x W 8.4
x D 3.97
Untreated
US $700
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Weight : 5.54
ct
Size (mm): L 15.6 x W 10.6
x
D 5.89
Untreated
US $500
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JUDGING
QUALITY
As with all other opals, the
most important consideration
for Mexican opal is the strength
of its rainbow-colored flashes.
Because the flashes change with
the viewing direction, it is
necessary to rotate the opal
and check the beauty and strength
of the colors from different
angles before making an overall
decision. Additionally, the
way the colors change as the
gem is rotated is itself an
important element of the stone's
beauty.
Next, the height of
the cabochon is important. If
an opal’s apex is either too
high or too low and flat, it
will lack a sense of elegance
when worn. Such a fault might
be overcome through exceptionally
well-conceived jewelry, but
it is important to beware of
extremely high or low cabochons,
especially when buying loose
stones. |
Cantera
Cantera (cantera de opalo) is
polished along with its rhyolite
(a type of jasper) matrix. It
has been on the market since
about 1980; before then, the
opal inside was polished without
the mother rock and used as
Mexican opal. Cantera has a
unique character, and it is
popular in the United States.
In terms of quantity, it currently
accounts for 60 percent of all
Mexican opal. |
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