Blue Chalcedony
Microcrystalline Quartz var. Blue Chalcedony · Semi-Precious Gemstone / Lapidary Material
Crystal System
Trigonal (specifically hexagonal under the microcrystalline scale); typically occurring in massive, botryoidal, or cryptocrystalline habits.
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of metal inclusions
Formation Process
Hydrothermal or Sedimentary. It forms through the precipitation of silica from water at low temperatures, filling cavities in volcanic rocks or occurring as nodules in sedimentary limestone.
About This Crystal
A translucent to opaque mineral with a waxy to vitreous luster. This specimen shows a dark base rock with distinctive streaks or bands of light blue to greyish-blue silica. The surface appears uneven with a slight conchoidal fracture pattern.
Physical Characteristics
Color: Blue, grey-blue, or white; Streak: White; Cleavage: None; Fracture: Conchoidal to splintery; Specific Gravity: 2.6–2.64; Fluorescence: Occasionally glows weak green or white under UV light.
Optical Properties
Refractive Index: 1.530–1.540; Birefringence: up to 0.009; Optical Phenomenon: Tyndall scattering (which causes the blue appearance) and occasionally slight adularescence in higher grades.
Hardness & Durability
Origin Region
Notable sources include Turkey, Namibia, Malawi, and the United States (Oregon/California); often found in volcanic cavities and sedimentary lining.
Hardness & Durability
Mohs Hardness: 6.5–7. It is quite durable and tough due to its interlocking fibrous structure, making it suitable for all types of jewelry.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid harsh chemicals and ultrasonic cleaners if the stone has surface-reaching fractures. Stable under sunlight but avoid extreme heat.
Rarity & Value
Common to Uncommon. Value depends on the intensity of the blue color and transparency. Stones with a deep, uniform blue without dark matrix are more prized; common rough specimens are affordable.
Special Characteristics
The blue color is often not caused by pigment but by the scattering of light (Tyndall effect) by tiny particles within the silica matrix.
Lore & History
Historically used in the ancient Mediterranean civilizations (Greece, Rome) for seals and amulets. In metaphysical traditions, it is known as the 'Speaker's Stone,' associated with the Throat Chakra and believed to foster calm communication.