Pure quartz, or “rock crystal” from Brazil. Source: Didier Descouens, CC BY-SA 4.0 Pick up a rock almost anywhere on Earth and chances are pretty good that there’s at least some quartz in it.

Geodes, for instance, are created when mineral-rich water seeps into hollow spaces within rock formations and slowly evaporates, leaving behind dazzling crystals like quartz and amethyst.

Right: OH-defects in young (0.3 Gyr) Variscan granites are one order of magnitude higher than in old (0.9-1.8 Gyr) Proterozoic granites from Scandinavia . The OH-content is reflected in recent ...

Evidence for the use of rock crystal - a rare type of perfectly transparent quartz which forms in large hexagonal gems - has occasionally been found at prehistoric sites in the British Isles, but ...

Large crystals found in geodes and other rocks are relatively rare. Pink ChalcedonyA pink chalcedony shows off its beauty. Chalcedonies include many types of cryptocrystalline quartz gems and ...

More than one of our readers suggested we highlight this beautifully-shot process documentary about the laborious and precise manufacturing of piezoelectric quartz crystals in the early 1940s.