Chalcedony
Quartz var. Chalcedony · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal, microcrystalline (cryptocrystalline) quartz habit forming in massive, nodular, or tumbled pebble forms
Mineral Group
Silicates, specifically Tectosilicates
Chemical Formula
SiO2
Formation Process
Hydrothermal and low-temperature deposition from silica-rich aqueous solutions circulating through volcanic and sedimentary rocks
About This Crystal
A tumbled, smooth pebble with a waxy to vitreous luster, translucent to semi-opaque appearance, exhibiting soft beige, creamy white, and light brownish-pink tones with concentric zoning and a central eye-like formation
Physical Characteristics
Body color ranges from white to grey, beige, and light brown; streak is white; no cleavage; conchoidal to uneven fracture; specific gravity around 2.60 to 2.65; brittle tenacity; generally inert to weak fluorescence under UV light
Optical Properties
Uniaxial positive with a refractive index of approximately 1.530-1.540; doubly refractive with very low birefringence; displays a sub-vitreous to waxy luster
Hardness & Durability
Origin Region
Found worldwide including Brazil, India, Madagascar, USA, and Uruguay; formed in low-temperature hydrothermal veins and volcanic cavities
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline interlocking structure; stable and durable for daily jewelry wear with no distinct cleavage
Care & Maintenance
Easy to clean with warm soapy water and a soft brush; avoid harsh chemicals and hydrofluoric acid; safe from standard household wear but should be stored separately to prevent scratching softer stones
Rarity & Value
Common and widely accessible; value depends on color, size, and pattern clarity, typically ranging from inexpensive tumbling stock to moderate collector specimen prices
Special Characteristics
Cryptocrystalline structure causing microfibrous quartz growth; may exhibit slight chatoyancy or banding patterns depending on the specific variety
Lore & History
Historically used across ancient civilizations for amulets, seals, and carvings; traditionally associated with emotional balance, nurturing, and grounding in modern crystal healing practices