TYPE O COLORS

In terms of quality, it is debatable as to which hue in the play-of-color is most valuable. It is said that red is most preferred, followed in order by orange, green, and blue, but it is also important that the stone be brilliant, of course, and that the colors be clear and vivid. Given equal conditions, red is considered the best hue. However, even the exact shade of red- an orangey, a pure red, or a purplish red- is seen as important, and since there are differences even within these hues, the final decision must be based on how attractive the color appears. Here we have compared grades S and D in red, orange, and blue. In D qualities, the color is dull and unattractive, making it irrelevant whether or not a red color appears. This is a common point in the evaluation of any type of gemstone. For example, it is futile to argue the rarity of color or lack of inclusions in a diamond that lacks brilliance.

As with light opal, the basis for evaluating the fineness of a black opal is the combination of brilliance and color. Strong colors and an overall brightness are absolute requirements for a high-quality black opal. Among stones with good appearance and shape, sufficient thickness, and absence of cracks (crazing), premium prices are given to those with strong play-of-color of red, orange, green, and blue, in that order. Furthermore, the shape of the pattern is important, with patterns of large mosaic patches considered more desirable than small pinpoint patterns. Of these, the more attractive patterns have specific names and are highly valued. Some black opals show totally different directions, such as yellow and green from one direction and red from another, or blue from one direction and green from another, and these are further valued for their rarity. Black opals have tones around 6 or 7, and the beauty grade is assigned using the brightness of color as a basis, taking into consideration such factors as appearance, shape, and the presence of cracks.