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Base
Color of Opal
The term "base
color" is often confused but it is really very simple. Think about looking
at an opal and extinguishing all the fire colors coming from it. What remains
is the base color of the stone. Base colors, sometimes called background colors,
include black, semi-black, crystal, semi-crystal, white, gray, blue, orange,
brown, boulder black and boulder brown. Base color is one of the four primary
characteristics which determine an opal's value.
Base color of an
opal is determined only by looking at the top of the stone. With your eye above
the stone, look down at the face of the opal as it rest on your table. Notice
that it has two color characteristics, the play of fire and a general base color.
It is the general base color we wish to determine now.
Base color is actually
a combination of three things: color or hue, body tone or saturation's, and
transparency or clarity. A complete description of a stone requires mention
of all three and each affects the stone's value.
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Black Opal
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A natural solid
opal which is opaque when viewed from the top of the stone, and which has
a play of color against a dark background graded as at least#3 Black on
the Lightning Ridge Miners Association Tone Scale, is graded as a black
opals. The back of the stone may be any color. |
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Black Crystal
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A natural solid
opal which is translucent to transparent with play of color which when viewed
from the top is graded as at least#3 Black on the Lightning Ridge Miners
Association Tone Scale. |
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Semi-Black
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A solid opal
which is translucent to opaque when viewed from the top and which has a
play of color against a dark gray background corresponding to semi-black
on the Lightning Ridge Miners Association Tone Scale. |
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Boulder
Black
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A natural boulder
opal which has a play of color against a dark opaque background graded as
at least #3 Black on the Lightning Ridge Miners Association Tone Scale.
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Crystal
Opal
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a solid opal
which is transparent showing a play of color and no base color. |
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Semi-Crystal
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A solid opal
which is translucent showing a play of color and a clear base color. |
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Gray Opal
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A solid opal
which is opaque or translucent showing a play of color on a gray base corresponding
to the gray tones on the Lightning Ridge Miners Association Tone Scale.
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White Opal
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A solid opal
which is opaque to translucent showing a play of color on a white to off-white
base color as graded as a white opal. |
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Light Opal
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In Australian,
opal graded as crystal, semi-crystal, white or gray are all under a general
category called "light opal." |
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Orange Opal
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A solid opal
which is translucent to opaque showing a play of color on an orange background.
This type of opal would be called red opal or yellow opal depending on the
base color. |
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Orange Crystal
Opal
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A solid opal
which is transparent showing a play of color on an orange background. This
type of opal would be called red crystal or yellow crystal depending on
the base color. This is generally referred to as fire opal. |
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Brown Crystal
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A solid opal
which is transparent showing a play of color on a brown base color. |
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Jelly Opal
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A solid opal
which is transparent showing no play of color, but it may show an opalescence
without a pattern. The orange material without a play of color from Mexico
is frequently seen in faceted stones, and would be termed orange jelly,
although it is also called fire opal in the industry. The blue jelly from
Australia is sometimes called blue bottle potch. |
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Blue Opal
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A solid opal
which can be translucent to opaque with or without a play of color on a
blue base color. The opaque blue common opal from the Andes is just call
"blue opal." There is also a pink variety of this common opal.
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Beautiful Australian Opals