Agate
Quartz var. Agate · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal, massive or microcrystalline cryptocrystalline habit
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2
Formation Process
Hydrothermal and secondary deposition in volcanic cavities or cavities of sedimentary rocks
About This Crystal
A tumbled, polished stone displaying dark green, brown, and ochre banding with a waxy to vitreous luster, translucent to opaque transparency, and characteristic concentric growth layers.
Physical Characteristics
Colors range from green to brown with banding; white streak; no true cleavage; conchoidal fracture; specific gravity around 2.60 to 2.65; brittle tenacity; typically inert under UV light
Optical Properties
Refractive index of 1.544 to 1.553; doubly refractive (aggregate); exhibits no significant pleochroism due to microcrystalline nature
Hardness & Durability
Origin Region
Found globally; notable sources include Brazil, India, Madagascar, and the United States
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline structure; durable and highly suitable for daily jewelry wear
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid harsh chemicals and prolonged direct sunlight to maintain color integrity
Rarity & Value
Common and widely accessible; value depends on color contrast, patterning, size, and cutting quality, with prices generally ranging from inexpensive to moderate
Special Characteristics
Microcrystalline quartz aggregate showing prominent color banding and healed fractures filled with secondary mineral matter
Lore & History
Historically used as an amulet for protection, grounding, and balancing emotional energy; associated traditionally with the root and heart chakras