Blue Chalcedony
Quartz var. Chalcedony · Semi-Precious Gemstone / Decorative Stone
Crystal System
Trigonal (Monoclinic component), typically occurring in microcrystalline or cryptocrystalline massive habits with a rounded, botryoidal structure.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron, aluminum, and nickel often influencing pigmentation.
Formation Process
Formed through the precipitation of silica-rich hydrothermal fluids in cavities of igneous rocks or through low-temperature groundwater processes in sedimentary layers.
About This Crystal
A translucent to semi-opaque cryptocrystalline quartz. Usually exhibits a soft, waxy luster and a sky-blue to lavender-blue color. This specific tumbled specimen shows color zoning and a milky, ethereal transparency with possible dendrite-like internal shades.
Physical Characteristics
Color: Pale blue to deep sky blue; Streak: White; Cleavage: None (absent); Fracture: Conchoidal to splintery; Specific Gravity: 2.6 – 2.64; Fluorescence: Often weak bluish or yellowish under LWUV.
Optical Properties
Refractive Index: 1.530 – 1.540; Birefringence: Up to 0.004; Pleochroism: Absent; Optical Character: Aggregates show no specific figure; Luster is vitreous to waxy.
Hardness & Durability
Origin Region
Namibia (famous for 'African Blue'), Turkey, India, Brazil, and Malawi. Forms in volcanic cavities and sedimentary environments.
Hardness & Durability
Mohs Hardness: 6.5 – 7. It is quite tough due to its microcrystalline structure, making it highly durable for jewelry use compared to single-crystal quartz.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic and steam cleaners as they may cause internal fractures. Store away from direct sunlight to prevent potential color fading in some varieties.
Rarity & Value
Common to Uncommon. Value is determined by color saturation (evenness), translucency, and origin. Untreated blue specimens from Namibia are highly sought after.
Special Characteristics
Tyndall scattering often provides a subtle bluish 'glow' or inner light. Occasionally exhibits faint banding (Agate-like) or darker inclusions of manganese oxides.
Lore & History
Historically used in Rome for seals and signet rings. In traditional lore, it is known as a stone of communication and calm, often associated with the Throat Chakra. It was historically believed to protect sailors from drowning.