Agate
Quartz var. Chalcedony (Agate) · Semi-Precious Gemstone and Decorative Stone
Crystal System
Trigonal, microcrystalline habit forming as rounded pebbles or nodules
Mineral Group
Silicates, specifically Tectosilicates
Chemical Formula
SiO2
Formation Process
Hydrothermal and secondary deposition processes filling cavities in volcanic and metamorphic rocks at low temperatures and pressures
About This Crystal
A tumbled, smooth, translucent to semi-translucent pebble featuring a pale greyish-white body with subtle banding and distinct reddish-brown mineral inclusions (such as hematite or iron oxide dots) scattered throughout
Physical Characteristics
Color is pale milky white with red spots; white streak; no cleavage; conchoidal fracture; specific gravity around 2.60 to 2.65; brittle tenacity; displays a waxy to vitreous luster when polished
Optical Properties
Refractive index ranges from 1.544 to 1.553; doubly refractive with very low birefringence; generally aggregate optical character showing no distinct pleochroism
Hardness & Durability
Origin Region
Found globally; notable sources include Brazil, India, Madagascar, Uruguay, and the USA (Lake Superior region)
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline interlocking structure; highly durable and suitable for everyday jewelry use
Care & Maintenance
Easy to care for; safe to clean with warm soapy water and a soft brush; avoid harsh chemicals and prolonged direct sunlight if dyed, though natural agate is generally stable
Rarity & Value
Common and widely available; value is low to moderate, depending on size, unique patterns, intensity of colors, and craftsmanship of the polish
Special Characteristics
Features distinct dotted or flecked iron oxide inclusions trapped within a chalcedony matrix, giving it a unique spotted appearance
Lore & History
Historically used by ancient civilizations like the Egyptians and Greeks for amulets, seals, and ornamentation; in modern crystal healing, it is traditionally associated with grounding, emotional balance, stability, and clearing negative energies