Dendritic Agate

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Translucent white to grey with black/brown tree-like patterns; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; SG: 2.58–2.64

Formation & Geological History

Formed when groundwater rich in manganese and iron oxides flows through cracks in white chalcedony or quartz, depositing mineral dendrites. Primarily formed in volcanic or sedimentary environments.

Uses & Applications

Used extensively in jewelry as cabochons, lapidary arts, collection specimens, and ornamental carvings.

Geological Facts

The term 'dendritic' comes from the Greek word 'dendron' meaning tree. Though they look like fossils, the patterns are purely mineral and contain no organic matter.

Field Identification & Locations

Identify by looking for 'moss' or 'branch' patterns within translucent chalcedony. Commonly found in Brazil, India, Madagascar, and the USA (notably Montana). To identify in the field, look for nodules with a waxy luster and high hardness.

Identified on: 4/13/2026

Mode: Standard