Moss Agate
Chalcedony var. Moss Agate (Cryptocrystalline Quartz) · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal (microcrystalline/cryptocrystalline); usually found in massive or nodular habits rather than distinct crystals.
Mineral Group
Silicates (Tectosilicate group, Quartz family)
Chemical Formula
SiO2 with inclusions of Hornblende, Chlorite, or Manganese/Iron Oxides
Formation Process
Hydrothermal/Sedimentary process where silica-rich fluids fill cavities in volcanic rock. The 'moss' inclusions form through the branching growth of mineral impurities like manganese or iron oxides during crystallization.
About This Crystal
A translucent to semi-opaque chalcedony containing dendritic, filaments, or moss-like inclusions of green, black, or brown. The base color is often milky white or bluish-grey. The luster is typically vitreous to waxy when polished.
Physical Characteristics
Color: Base is colorless/white/grey with green or brown inclusions. Streak: White. Cleavage: None. Fracture: Conchoidal to uneven. Specific gravity: 2.58–2.64. Non-fluorescent generally, though some matrix may show minor reaction.
Optical Properties
Refractive Index: 1.530–1.543. Birefringence: Up to 0.004. It is aggregate-polarizing. No pleochroism. The main optical appeal is the depth created by the inclusions within the translucent medium.
Hardness & Durability
Origin Region
Major deposits in India, Brazil, Uruguay, USA (Montana), and Australia. Typically found in volcanic rocks as cavity fillers.
Hardness & Durability
Mohs hardness: 6.5–7. It is tough and durable with no cleavage, making it excellent for daily wear in jewelry like the heart-shaped carving shown.
Care & Maintenance
Safe to clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if the stone has significant surface-reaching fractures or druzy pits. Generally stable in sunlight but avoid harsh acids.
Rarity & Value
Relatively common and affordable. Value is determined by the complexity and beauty of the 'landscapes' formed by the inclusions. Prices range from a few dollars for small tumbled stones to higher for large, artistic carvings.
Special Characteristics
Dendritic/moss-like inclusions that mimic organic plant life. This specimen shows a carved heart shape and appear to have small 'druzy' vugs or pits where tiny quartz crystals remain unpolished.
Lore & History
Historically used as an amulet for agriculture and gardens. In traditional lore, it is associated with new beginnings, grounding, and the heart chakra. It was valued by ancient civilizations for its perceived connection to nature.