The distinctiveness and color displayed by these segments determines the quality of an opal’s pattern. The pattern of colored segments that form the play of color of a precious opal is unique to each individual opal. This ranges from brilliant and bright to subdued and dull. Red coloring is caused by larger, rarer constructions of microscopic silica spheres, whereas blue is caused by the more common small spheres.īrilliance refers to the brightness and clarity of the colors displayed by an opal, when the stone is viewed face-up. Nature does not produce a red color as often as it does a blue or green. Red (fire) opal is generally more valuable than a mainly green opal, which in turn is more valuable than a stone showing only blue color. It is caused by the diffraction of white light across the internal structure of orderly arrayed spheres of silica, and produces the brilliant spectrum of colors the opal is known for. The phenomenon known as the play of color is the primary attraction of the opal. Some crystal opals display color so intense and dark that they are referred to as black crystal opals. The term crystal opal refers to the 'diaphaneity' (transparency) of an opal, not its crystal structure, and is defined as any type of opal that is translucent or transparent.

Boulder opals also have a dark body tone but are not quite as valuable, while white opals have a light body tone and are generally the least valuable form of opal. Generally, opals with a black or dark body tone are more valuable than those with a white, light, or crystal body tone, because a stone with a darker body tone tends to display colors more vibrantly.īlack opal is the most prized type of opal and may earn prices over $10,000 USD a carat. It refers to the background or the underlying color of the opal, which ranges from dark to light.

Doublets and triplets are 'assembled' stones that only contain a very thin slice of natural opal and are therefore generally much less valuable.īody tone is one of the most important factors in the classification and valuation of opals. An opal doublet or triplet can be worth considerably less than a solid opal. It is essential to first identify the type of opal that is being valued. The overall carat size of the stone will then determine the price of the opal. When being valued, an opal is carefully examined and given a price per carat. Other important variables to consider include the quality of the cut and polish, and the size of the stone. The type of opal, body tone, brilliance, pattern, color bar thickness, play of color, and faults all play important roles in determining the value. An opal’s worth is a difficult thing to measure.

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