Agate / Jasper
Quartz var. Chalcedony · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, massive to microcrystalline habit
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2
Formation Process
Hydrothermal and sedimentary deposition from silica-rich solutions filling cavities in host rocks
About This Crystal
An opaque to translucent nodular specimen featuring distinct banded patterns with shades of grey, cream, brown, and dark dendritic inclusions. The surface is smooth with a waxy luster.
Physical Characteristics
Colors include grey, brown, white, and black; white streak; no cleavage; conchoidal fracture; specific gravity around 2.65; brittle tenacity; generally inert to UV light
Optical Properties
Singly to doubly refractive with microcrystalline aggregate structure; refractive index approximately 1.530 to 1.540; no pleochroism
Hardness & Durability
Origin Region
Worldwide, notably Brazil, USA, Madagascar, and India; forms in volcanic cavities and sedimentary rock
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness; stable and suitable for everyday jewelry wear
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid harsh chemicals and sudden temperature shocks; store away from harder gems to prevent scratching
Rarity & Value
Common and widely available; value depends on pattern, size, color contrast, and polish; generally inexpensive
Special Characteristics
Distinct natural banding, potential fortification patterns, and localized dendritic or inclusion features
Lore & History
Historically used by ancient civilizations for amulets, seals, and ornaments; associated with grounding, emotional balance, and stability in modern crystal lore