Boulder opals also have a dark body tone, but they are not as valuable, while white opals have a light body tone and are generally the least valuable form of opal. Color is the first thing you'll notice about an opal. Red is the rarest and most sought after color. In order of value, the most valuable color is red, then orange, green, blue and purple.
However, opal is usually not a single color. It is important to decide which is the dominant color followed by the secondary colors. Use the dominant color as the color that will affect the price. Here, the manager of Gem-A Instruments, Samatha Lloyd FGA EG, provides a quick but essential guide to the value factors of opal and what distinguishes a fantastic specimen from an average one.
There are a number of factors that alter the value of opals. As mentioned, black opal may have higher prices than light opal (especially with a tinted black body tone), although this is not to say that a fantastic light opal can't be more expensive than a mediocre black opal. Opals are in a class by themselves. As a species, opal is so unique that it has its own descriptive vocabulary.
More than any other gem, each opal is distinctly individual. Opals are also the most delicate gemstones that are commonly used and require special care. As opals grow by filling cavities in the earth, they sometimes take the form of pieces of wood, bones and seashells buried in the ground. Though once known as “bad luck”, opals are quickly becoming one of the most sought-after gemstones in jewelry collections.
Black Opal Opal Boulder Opal Ethiopian Crystal Opal. From semi-transparent to translucent with a rolling and moving light effect, sunflower opals resemble moonstones The Opal Body Tone Guide was approved by the Opal Association of Australia and intended to be a guide for Black Opal and Boulder opals. It is also important to remember that doublets and triplets do not have the same value as a solid opal. The “dominant color” of an opal can affect its value, with red having the highest cost, followed by orange, yellow, green, blue, indigo and violet.
Body tone refers to the background or “underlying color” of opal, ranging from black to dark to light. Opal is an amorphous form of silica, chemically similar to quartz, but containing between 3% and 21% water within its mineral structure. The thickness of the color bar in opal is relative to the overall size and shape of the individual stone. Scenes of nature and animals were popular motifs in Art Nouveau jewelry, and opal gems were popular jewelry stones during this period.
Discovered around 1900 in Virgin Valley, Humboldt County, Nevada, opal appears here as cracks and seams in opalized wood. Compared to ordinary opal, which is usually single color, black opal exhibits many different colors in contrast to a dark body tone. Extremely rare, the asterism or star effect shown by these opals is due to imperfections in the arrangement of their silicate spheres. It is important to be able to choose a doublet opal compared to a solid and this can be difficult when the opal is set in jewelry.
Fundamentally, opals from this region have a lower water content, which means that they are less susceptible to desiccation and less likely to exhibit “cracks” - fine fractures that affect the durability of the stone.
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