Agate (Blue Lace/Chalcedony vein)
Quartz var. Chalcedony (Agate) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal (Microcrystalline); mass is cryptocrystalline and typically occurs in nodular or vein-like habits.
Mineral Group
Silicates (Tectosilicates); Quartz group
Chemical Formula
SiO2 (Silicon Dioxide) with trace inclusions
Formation Process
Hydrothermal; silica-rich fluids deposit layers of chalcedony within gas vesicles or fractures of igneous rocks at low to moderate temperatures.
About This Crystal
The specimen shows a rough, dark basaltic matrix with a translucent bluish-white vein of chalcedony. It features a waxy to vitreous luster and distinct banding typical of agate formation.
Physical Characteristics
Color: Blue-white to grey; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58–2.64; Fluorescence: Often greenish or yellowish under shortwave UV.
Optical Properties
Refractive Index: 1.530–1.543; Birefringence: Up to 0.004; Optical Sign: Uniaxial (+); Non-pleochroic; Singly to doubly refractive (aggregate).
Hardness & Durability
Origin Region
Brazil, Uruguay, Namibia, and USA (Oregon/Washington). Found in volcanic host rocks (basalt/andesite cavities).
Hardness & Durability
Mohs Hardness: 6.5–7.0; Toughness: Very Good (no cleavage); Stable to light but can be sensitive to thermal shock.
Care & Maintenance
Clean with warm soapy water. Generally durable but avoid ultrasonic cleaners if there are internal fractures; keep away from harsh chemicals.
Rarity & Value
Common; Value factor is based on color saturation and banding clarity. Raw specimens are inexpensive collector items.
Special Characteristics
Displays microcrystalline banding known as agatescence; some specimens may show slight translucency or 'ghost' banding when back-lit.
Lore & History
Historically used for hardstone carving and amulets since the Neolithic era. In folklore, it is associated with cooling energy and calm communication (Throat Chakra).