Quartz, silicon dioxide (SiO2) is one of the most common minerals in the Earth’s crust, and occurrences of massive quartz (so-called “bull quartz,” in miners’ jargon) are common. They are distinctive, the white quartz typically standing out prominently from the background of ordinary rock, and bull quartz also sometimes hosts valuable mineral deposits. The gold in the hard-rock mines of the Mother Lode on the west slope of the Sierra Nevada, for example, typically occurs in quartz. So, when this large quartz deposit was discovered not long after the Gold…
