Moss Agate (Yellow-Brown variety)
Quartz (Chalcedony) var. Agate · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal (Hexagonal) system; microcrystalline/cryptocrystalline habit with dendritic and moss-like inclusions
Mineral Group
Silicates (Subgroup: Tectosilicates)
Chemical Formula
SiO2 (Silicon Dioxide) with inclusions of iron oxides (Goethite/Hematite) and manganese
Formation Process
Sedimentary/Hydrothermal: Forms via the slow deposition of silica-rich fluids in rock cavities at low temperatures, trapping moss-like mineral inclusions during growth.
About This Crystal
A translucent to opaque chalcedony featuring dendritic, branch-like, or mossy inclusions. This specimen shows a honey-brown to ochre base with cloudy white plumes and earthy brown matrix. Luster is vitreous to waxy.
Physical Characteristics
Color: Brown, yellow, and white plumes; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64; Luster: Vitreous; Fluorescence: Often inert but can show dull green/yellow under UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: Up to 0.009; Pleochroism: None; Optical Character: Uniaxial positive. Isotropic aggregate distribution.
Hardness & Durability
Origin Region
Notable sources include Brazil, India, USA (Montana, Wyoming), and Central Europe. Typically found in volcanic basalt cavities or sedimentary deposits.
Hardness & Durability
Mohs Hardness: 6.5-7. Durable and tough due to its cryptocrystalline structure; no cleavage makes it resistant to chipping.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners and harsh chemicals. Stable in sunlight but should be stored separately from harder stones like Topaz or Diamonds.
Rarity & Value
Common to Uncommon. Value is determined by the complexity and beauty of the 'moss' patterns. Often very affordable but high-quality dendritic patterns can command premium prices.
Special Characteristics
Features dendritic inclusions (iron/manganese) that mimic organic moss or plant life. This specimen displays plume-like white regions known as 'cloud agate' or 'plume agate' structures.
Lore & History
Historically used as a stone of agriculture and prosperity by ancient civilizations. In traditional lore, it is associated with grounding, stability, and connection to nature. Often used in talismans for new beginnings.