Agate
Quartz var. Chalcedony (Agate) · Semi-Precious Gemstone and Decorative Stone
Crystal System
Trigonal, microcrystalline habit forming in concentric bands or masses
Mineral Group
Silicates, specifically Tectosilicates
Chemical Formula
SiO2
Formation Process
Hydrothermal or sedimentary deposition in cavities of volcanic rocks, typically at low temperatures
About This Crystal
A polished, smooth cabochon-like tumbled stone exhibiting translucent teal, green, and brownish-yellow hues with distinctive curved color banding and smooth, glossy luster
Physical Characteristics
Color ranges from green, teal to yellow-brown; white streak; no cleavage; conchoidal fracture; specific gravity around 2.60 to 2.65; brittle tenacity; vitreous to waxy luster
Optical Properties
Refractive index ranges from 1.544 to 1.553; doubly refractive (uniaxial positive); translucent to opaque; exhibits aggregate optical properties
Hardness & Durability
Origin Region
Found globally; notable sources include Brazil, India, Madagascar, Uruguay, and the USA
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline interlocking structure; stable under normal conditions; well-suited for jewelry use
Care & Maintenance
Clean with warm soapy water and a soft cloth; avoid harsh chemicals and prolonged exposure to direct sunlight to prevent color alteration; store separately from harder gems like corundum or diamond
Rarity & Value
Common and widely available; value depends primarily on color saturation, patterning, size, and cutting quality; typically affordable with higher-end patterned specimens fetching moderate prices
Special Characteristics
Displays concentric or planar color banding, occasionally chatoyant or featuring inclusion patterns like mossy or dendritic formations
Lore & History
Historically used by ancient civilizations such as the Egyptians and Greeks for amulets, seals, and ornaments to ward off evil and promote harmony; traditionally associated with grounding, emotional balance, and the heart chakra in metaphysical practices