Blue Quartz: Mineral information, data and localities.

An opaque to translucent, blue variety of quartz, owing its colour to inclusions, commonly of fibrous magnesioriebeckite or crocidolite, or of tourmaline.

Blue Quartz – Mineralogy

Sillimanite - an overview

Earth's Rocks Contain a Hidden Ocean's Worth of Water

Dark crystals: the brutal reality behind a booming wellness craze, Health & wellbeing

Igneous Rocks - Geology (U.S. National Park Service)

Celestine: Mineral information, data and localities., ralf morales ojo