When evaluating opals, what aspect should be considered as separate from its play-of-color?

When evaluating opals, the background color is an important aspect to consider separately from the play-of-color. The play-of-color refers to the vibrant flashes and changes of color that result from the unique internal structure of opal, which creates a phenomenon known as opalescence. The background color, however, is the base hue that underlies the play-of-color and can significantly impact the overall appearance and desirability of the stone.

Different background colors can either enhance or contrast with the play-of-color, affecting the stone's visual impact. For example, a black opal, which has a dark background color, can make the play-of-color appear more vivid and striking. Conversely, lighter background colors may produce a softer appearance. Therefore, understanding the relationship between the background color and the play-of-color is crucial for assessing the quality and value of an opal.

While specific gravity, technological enhancements, and market demand are all relevant factors in evaluating opals, they do not directly influence the aesthetic quality and visual interplay of colors that are derived from the opal's play-of-color and its underlying background.