October’s birthstone can be a bit confusing: what is “precious” opal, anyway? Is it different from fire opal? And what kinds of opals are “common”? This post is a short primer for all your opal terminology needs.
The most famous precious opal in the US comes from Virgin Valley in Humboldt County, Nevada. Petrified tree trunks buried in volcanic tuffs have developed opals with gorgeous play of color.
In this specimen, white common opal infills large holes, while blue and green precious opal is found in pores preserving the tree trunk’s original grain structure. This specimen is from Richard and Helen Rice’s original family collection.
Have you ever collected opal from Virgin Valley? Where are some of your favorite opal localities?
This is part of our What’s in the box? series.