Chalcedony (Moonstone variant or White Agate)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Translucent white to pale blue; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.58–2.64

Formation & Geological History

Formed from the deposition of silica from water at relatively low temperatures in cavities of both igneous and sedimentary rocks. It common develops in volcanic pockets as a primary or secondary mineral.

Uses & Applications

Commonly used in jewelry (cabochons and beads), ornamental carvings, and historical artifacts like seals and amulets. It is also used as an industrial abrasive in some forms.

Geological Facts

Chalcedony was one of the first materials used by early humans to make tools like arrowheads and scrapers due to its conchoidal fracture pattern which creates sharp edges. In ancient Rome, it was highly prized for engraving signet rings because hot wax would not stick to it.

Field Identification & Locations

Identify by its waxy luster, translucency, and inability to be scratched by a steel knife. It often occurs as botryoidal (grape-like) masses or nodules in the field. Found globally, with notable deposits in Brazil, India, and the Western USA.

Identified on: 4/18/2026

Mode: Standard