Agate (Moss or Dendritic Agate)

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Translucent gray or white with dark brown or black inclusions; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58–2.64.

Formation & Geological History

Formed in volcanic or metamorphic environments when silica-rich fluids permeate rock cavities or fractures. The inclusions (dendrites) are branched patterns formed by manganese or iron oxides during the stone's formation over millions of years.

Uses & Applications

Primary uses include jewelry (cabochons, beads), decorative lapidary arts, and collecting. Historically used for making healing amulets and hard-wearing seals.

Geological Facts

Despite their appearance, the moss-like or leaf-like patterns inside are purely inorganic minerals and not petrified organic matter. They are often called 'The Gardener's Stone' in folklore.

Field Identification & Locations

Identify in the field by its hardness (will scratch glass), waxy appearance when wet, and characteristic internal patterns visible when held to a light source. Commonly found in riverbeds and areas with volcanic rock history.

Identified on: 4/24/2026

Mode: Standard