Agate (Eye Agate)
Quartz var. Agate (Microcrystalline Chalcedony) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal/Hexagonal system; typically forms in massive, microcrystalline (cryptocrystalline) habits with fibrous radial textures.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide)
Formation Process
Hydrothermal/Sedimentary: Forms via the deposition of silica from groundwater in the cavities of igneous rocks or through replacement in sedimentary environments.
About This Crystal
A translucent to opaque cabochon displaying concentric banding. This specific specimen exhibits 'eye' patterns in shades of grey, lavender, and white with a vitreous to waxy luster and smooth polished surface.
Physical Characteristics
Color: Grey-lavender with white bands; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.6–2.7; Fluorescence: Often inert but can show yellowish-green under UV.
Optical Properties
Refractive Index: 1.530–1.540; Birefringence: Up to 0.009; Optical Character: Aggregate (Singly Refractive in practice); No significant pleochroism.
Hardness & Durability
Origin Region
Brazil, India, Botswana, and Uruguay; typically found in volcanic cavities (vugs) or ancient sedimentary deposits.
Hardness & Durability
Mohs Hardness: 6.5–7; Toughness: Very high due to the interlocking microcrystalline structure; makes it excellent for jewelry wear.
Care & Maintenance
Wash with warm soapy water and a soft brush; avoid hydrofluoric acid; generally stable under sunlight but dyed varieties may fade.
Rarity & Value
Common; Value is determined by the uniqueness of the banding patterns ('eyes'), color contrast, and size. Unprocessed natural colors are preferred.
Special Characteristics
Concentric 'Eye' banding (orbital marking); may show 'iris' agate effects if sliced very thin (diffraction), though not visible in this cabochon.
Lore & History
Historically used in amulets to ward off the 'evil eye' in ancient Mediterranean cultures. Traditionally associated with grounding, protection, and emotional stability in crystal healing practices.