Green Opal
Opal var. Common Green Opal (Amorphous silica) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Amorphous (Non-crystalline); typically occurs in massive, botryoidal, or vein-filling habits with a conchoidal fracture.
Mineral Group
Silicates (Tectosilicate class, though non-crystalline mineraloid)
Chemical Formula
SiO2·nH2O (Hydrous silicon dioxide, with trace nickel or iron for green coloring)
Formation Process
Sedimentary/Hydrothermal: Formed from silica-rich water percolating into rock cavities and fissures at relatively low temperatures, solidifying into a gel that hardens over millennia.
About This Crystal
The specimen is an olive to lime green 'common opal' (non-precious). It exhibits a characteristic waxy to Vitreous luster, translucent to opaque transparency, and a smooth, shell-like conchoidal fracture surface visible in its broken edges.
Physical Characteristics
Color: Olive green; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 1.9–2.3; Tenacity: Brittle; Fluorescence: May glow inert to faint green under UV.
Optical Properties
Isotropic (Singly refractive); Refractive Index: 1.42–1.47; No pleochroism or dispersion; Lacks the 'play of color' (fire) found in precious opal.
Hardness & Durability
Origin Region
Madagascar, Tanzania, Brazil, and Peru. Often found in volcanic cavities or as a replacement in sedimentary rock.
Hardness & Durability
Mohs Hardness: 5.5–6.5. It is relatively soft and brittle compared to quartz, making it sensitive to impact and pressure.
Care & Maintenance
Clean with warm soapy water only; avoid ultrasonic or steam cleaners. Store away from direct sunlight and heat to prevent dehydration and cracking (crazing).
Rarity & Value
Common; Value is determined by color intensity and size. Generally inexpensive as a mineral specimen, but polished pieces can carry a premium for jewelry.
Special Characteristics
Often contains dendritic inclusions or internal 'mossy' patterns. This specimen shows a waxy luster and classic 'wet look' associated with hydrous silica.
Lore & History
Historically used as a stone of rejuvenation and emotional recovery. In traditional lore, it is associated with the Heart Chakra and believed to help one process feelings of grief or stress.