Opals are often divided into types based on background color. Courtesy Mariora, Surfer’s Paradise, Australia This black opal has a lot of red play-of-color, which is considered highly desirable. Background color-also called bodycolor-is caused by the suspension of tiny impurities within opal’s silica spheres. Opal displays background color in addition to play-of-color.

An opal might display a single color, two or three colors, or all the colors of the rainbow. Look for the presence of matrix, crazing, pits, etc.Ĭonsider the opal’s symmetry, thickness, polish, sizing and calibration. Is it transparent, semi-transparent, translucent, semi-translucent or opaque? Is it a black opal, white opal, crystal opal, etc.?ĭetermine the ratio and quality of its play-of-color:Ĭonsider the percentage of play-of-color compared to background color, its intensity, dominant hues, range of color and pattern. Rotating the opal against a background helps when you’re determining its type and evaluating its play-of-color and cut. Opal evaluation should be done under controlled lighting on a dark background. Clarity-Transparency and quantity of inclusions.Color-Background color and play-of-color.There are three main aspects of an opal’s quality: As diverse as snowflakes or fingerprints, each gem can differ noticeably. Individual opals can vary widely in appearance and quality. Small play-of-color flashes of orange and green predominate in a pinfire pattern, with spots of a more muted blue over a grayish bodycolor. This large Australian light opal cabochon weighs 117.85 carats. Comprehensive CAD/CAM For Jewelry Certificate

Opal crystal