Agate (specifically Blue Lace or Chalcedony Agate)
Quartz var. Agate (IMA: Quartz) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal/Hexagonal system in microcrystalline (cryptocrystalline) form; Habit is typically massive, banded, or nodular
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide) with microcrystalline structure
Formation Process
Hydrothermal/Sedimentary process: Silica-rich groundwater percolates into cavities in volcanic rock, depositing layers of microcrystalline quartz over time from the outside-in
About This Crystal
Translucent to semi-opaque specimen exhibiting distinct parallel banding in shades of periwinkle blue, lavender, and grey. Features a waxy to vitreous luster on the polished surface with a dull, earthy exterior matrix. The interior shows a small druzy or micro-crystalline quartz core
Physical Characteristics
Color: Blue, grey, and white; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58–2.64; Fluorescence: May show weak yellow or green under UV light
Optical Properties
Refractive Index: 1.530–1.540; Birefringence: Up to 0.004; Optical character: Aggregate; Phenomena: Tyndall scattering (contributes to blue hue)
Hardness & Durability
Origin Region
Brazil, Uruguay, Namibia, and India; often found in volcanic host rocks and basaltic cavities
Hardness & Durability
Mohs hardness: 6.5–7.0; Toughness: High (very durable due to cryptocrystalline structure); Stability: Stable but can be damaged by hydrofluoric acid
Care & Maintenance
Safe to clean with warm soapy water; generally safe for ultrasonic cleaners unless there are visible fractures. Avoid harsh chemicals and prolonged direct sunlight for dyed varieties
Rarity & Value
Common; Value is determined by the clarity of banding and intensity of color. High-quality Blue Lace Agate is more sought after but generally affordable
Special Characteristics
Prominent concentric banding (agate layering); includes a small internal vug with micro-quartz crystals; colors are influenced by the scattering of light within the microscopic fibers
Lore & History
Historically used in amulets since Ancient Greece for protection. In metaphysical lore, it is known as a stone of communication and cooling energy, often associated with the Throat Chakra