Agate

The stone was named after the river Achates, where colorful agates were obtained in the ancient times. It is a microcrystalline and cryptocrystalline variety of the quartz group (crystals are visible only through microscopic examination), usually translucent in thin slices, otherwise opaque. The beauty of its stripey appearance can be highlighted by cutting it en cabochon.

Basic properties

Composition	SiO₂
Class	Oxydes and hydroxydes
Crystal system	Trigonal
Mohs' hardness	7
Fracture	Conchoidal
Cleavage	None
Lustre	Glassy
Streak	White
Localities	Brazil, Uruguay (Artigas), Germany (Rochlitz), India (Gujarat), Madagascar, Mexico, USA (Florida)