One variety of this mineral was used to create the most perfect sphere in human history, and another is found at areas which 
One variety of this mineral was used to create the most perfect sphere in human history, and another is found at areas which saw immense pressure, like nuclear bomb tests and the K-T event. In addition to the "fused" and (*) "shock" varieties, colorful instances of this mineral are sometimes called citrine, "rose", or the purple amethyst. Composed of one silicon atom for every two oxygen atoms, this is, for ten points, what second most common mineral in the Earth's crust after feldspar?
One variety of this mineral was used to create the most perfect sphere in human history, and another is found at areas which saw immense pressure, like nuclear bomb tests and the K-T event.
{Quartz}