Amethyst is a type of quartz, a mineral composed of silicon dioxide (SiO₂). Quartz is one of the most abundant minerals in the Earth’s crust, forming in a variety of geological environments. However, ...

Quartz also has the benefit of coming in a variety of colors, especially on the lighter side of the spectrum. Both crisp and ...

I share the reluctance of modern petrologists to propose new variety names for rocks. There are, however, cases in which a variety name is justifiable to imply a significant physical, chemical or ...