When we talk about crystals around here, we’re generally talking about the quartz variety used to make oscillators more stable, or perhaps ruby crystals used to make a laser. We hardly ever talk ...

Evidence for the use of rock crystal - a rare type of perfectly transparent quartz which forms in large hexagonal gems ... a mile south of another dig at Arthur’s Stone. There, they studied a complex ...

Chalcedonies include many types of cryptocrystalline quartz ... form beautiful crystals, but the most prized of all are gemstones. Uncut gems often look fairly ordinary–like rocks.

Gem(stone): A precious or semiprecious stone ... leaving behind dazzling crystals like quartz and amethyst. Crystals also form when heat and pressure cause minerals to recrystallize, resulting ...