Agate (Banded Jasper/Chalcedony)
Quartz var. Chalcedony · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, microcrystalline habit forming in masses, crusts, and nodules
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2
Formation Process
Hydrothermal deposition and low-temperature precipitation in cavities of volcanic and sedimentary rocks
About This Crystal
A polished slab displaying parallel linear banding in warm brown, tan, and cream tones, with a translucent to opaque appearance and a waxy to vitreous luster
Physical Characteristics
Color ranges from brown to white with parallel bands; white streak; no cleavage; conchoidal fracture; specific gravity around 2.60 to 2.65; brittle tenacity; generally inert to weak fluorescence under UV light
Optical Properties
Refractive index ranges from 1.544 to 1.553, uniaxial positive birefringence, aggregate optical character with no significant pleochroism
Hardness & Durability
Origin Region
Worldwide, notably Brazil, India, Madagascar, and the United States
Hardness & Durability
Mohs hardness of 6.5 to 7, good toughness, high chemical stability, highly durable for general jewelry and decorative use
Care & Maintenance
Clean with warm soapy water using a soft brush; avoid harsh chemicals and sudden thermal shock; safe from standard sunlight fading
Rarity & Value
Common and widely available, with value depending on color vividness, pattern uniqueness, polish quality, and size, ranging from inexpensive to moderate for fine specimens
Special Characteristics
Fine microscopic quartz crystal structure (chalcedony) featuring distinct linear deposition banding
Lore & History
Historically used across ancient civilizations for amulets, seals, and ornaments; traditionally associated with grounding, emotional stability, and the root chakra in modern crystal lore