Agate (Moss or Dendritic variety)
Quartz var. Agate (Microcrystalline Quartz) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal/Hexagonal system; Microcrystalline/Cryptocrystalline habit
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2 (Silicon Dioxide) with impurities of Fe and Mn
Formation Process
Hydrothermal deposition of silica-rich fluids within rock cavities (geodes) or fractures, often during volcanic cooling
About This Crystal
Translucent to opaque chalcedony featuring intricate, organic, or swirling patterns in shades of white, grey, and mossy brown-green. Luster is waxy to vitreous.
Physical Characteristics
Color: White, grey, and earth tones; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58–2.64; Non-fluorescent to weakly yellow.
Optical Properties
Refractive Index: 1.530–1.543; Birefringence: Up to 0.004; Singly refractive (aggregate); No notable pleochroism.
Hardness & Durability
Origin Region
Brazil, India, USA (Montana), and Madagascar; found in volcanic cavities or sedimentary nodules
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: Excellent due to microcrystalline structure; Highly durable for all jewelry types.
Care & Maintenance
Wash with warm soapy water; avoid harsh chemicals like hydrofluoric acid. Stable in sunlight but sensitive to extreme thermal shock.
Rarity & Value
Common; Value is determined by the uniqueness and aesthetic appeal of the internal patterns (scenic or dendritic features).
Special Characteristics
Displays 'moss-like' or 'dendritic' inclusions caused by manganese or iron oxides growing in branching patterns during formation.
Lore & History
Historically used for cameos and amulets in Ancient Greece and Rome. Traditionally associated with grounding, stability, and connection to nature.