Chalcedony
Quartz var. Chalcedony · Semi-Precious Gemstone and Decorative Stone
Crystal System
Trigonal, cryptocrystalline, typically forming in massive, botryoidal, or nodular habits
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2
Formation Process
Low-temperature hydrothermal deposition and precipitation from silica-rich aqueous solutions in cavities of volcanic rocks
About This Crystal
An oval-shaped cabochon featuring a smooth, polished surface with a waxy to vitreous luster. The specimen exhibits a translucent to semi-translucent body with pale blue-grey tones and subtle whitish banding or internal fracture lines reflecting light.
Physical Characteristics
Color ranges from pale blue, grey, to white; white streak; no true cleavage; conchoidal to uneven fracture; specific gravity of approximately 2.58 to 2.62; brittle tenacity
Optical Properties
Uniaxial positive with low birefringence (0.009); aggregate optical property showing general aggregate interference figures; translucent transparency
Hardness & Durability
Origin Region
Found worldwide including Brazil, India, Madagascar, USA, and Uruguay; forms in volcanic cavities and hydrothermal veins
Hardness & Durability
Mohs hardness of 6.5 to 7; good toughness due to microcrystalline interlocking structure; suitable for daily jewelry wear with proper settings
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid harsh chemicals, ultrasonic cleaners, and prolonged exposure to extreme heat or direct sunlight
Rarity & Value
Common; widely accessible and affordable, though fine translucent blue varieties or chatoyant specimens command higher prices; often dyed or heat-treated
Special Characteristics
Microcrystalline structure with cryptocrystalline quartz fibers; can occasionally show slight chatoyancy or banding patterns depending on the specific variety
Lore & History
Historically used in ancient civilizations for intaglios, seals, and protective talismans; in modern crystal lore, it is associated with emotional balance, calm energy, and communication, traditionally linked to the throat chakra