An Interview with Virginia Gillerman An Interview with Virginia Gillerman Virginia Gillerman is the research geologist for the Idaho Geological Survey. Idaho had a traumatic past, which helps account for our diversity of gems. There are a wide variety of geologic terrains in the state. That's why we get something like the garnet, which forms at great depths, and something like opal, which forms on the surface.
Gems are actually a subset of minerals, which are common building blocks of all of Idaho's rocks.
Quartz is one of the common minerals in Idaho, but only a few forms of quartz are valuable as gemstones. The difference has to do with the color of the stone, the clarity, the transparency, whether it's free from fractures, and the hardness. Often it has to do with the interaction of hot water with the rocks. The simplest example is petrified wood. Sometimes they are called thunder eggs.