Black Obsidian
Obsidian (Volcanic Glass) · Semi-Precious Gemstone / Igneous Rock
Crystal System
Amorphous (Non-crystalline); lacks a structured crystal system because it cools too rapidly to grow crystals.
Mineral Group
Amorphous Silicate (Mineraloid / Volcanic Glass)
Chemical Formula
70–75% SiO2, plus MgO, Fe3O4
Formation Process
Igneous (Extrusive); forms when high-silica felsic lava cools extremely rapidly upon contact with air or water, preventing atomic arrangement into a crystal lattice.
About This Crystal
A jet-black, opaque to slightly translucent sphere with a high vitreous (glassy) luster. The surface is smooth and reflective without visible grains, typical of high-quality polished obsidian.
Physical Characteristics
Color: Jet black; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like curves); Specific Gravity: 2.35–2.60; Fluorescence: Generally inert under UV.
Optical Properties
Refractive Index: 1.45–1.55; Birefringence: None (isotropic); Single refraction. Some varieties exhibit sheen (Gold/Silver Sheen) or iridescent colors (Rainbow Obsidian).
Hardness & Durability
Origin Region
Mexico (notably Jalisco), USA (Oregon, California), Iceland, and Italy (Lipari). Found in areas with geologically recent volcanic activity.
Hardness & Durability
Mohs Hardness: 5.0–5.5; Toughness: Low (brittle); Stability: Stable but sensitive to sudden temperature changes; prone to scratching by harder minerals like quartz or beryl.
Care & Maintenance
Clean with warm soapy water and a soft cloth. Avoid ultrasonic cleaners or steam. Store separately to prevent scratching, and protect from impact as it chips into razor-sharp edges.
Rarity & Value
Common; Value is generally low for black obsidian, though prices increase for 'Gold Sheen' or 'Rainbow' varieties. Largely used for lapidary work and affordable jewelry.
Special Characteristics
Distinctive conchoidal fracture pattern and vitreous luster. While this specimen appears solid black, it may reveal subtle mahogany streaks or a 'sheen' effect when viewed under intense light.
Lore & History
Historically used by ancient civilizations for mirrors (Aztecs) and lethal weaponry (arrowheads/scalpels) due to its razor-sharp edges. Metaphysically associated with protection, grounding, and the root chakra.