igneous
Black Obsidian
Volcanic Glass (felsic)
Hardness: 5-5.5 on the Mohs scale. Color: Deep black, sometimes with brown or gray undertones. Luster: Vitreous (glassy). Crystal structure: Amorphous (non-crystalline). Cleavage: Conchoidal fracture. Specific gravity: 2.35-2.60.
- Hardness
- 5-5
- Color
- Deep black, sometimes with brown or gray undertones
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 5-5.5 on the Mohs scale. Color: Deep black, sometimes with brown or gray undertones. Luster: Vitreous (glassy). Crystal structure: Amorphous (non-crystalline). Cleavage: Conchoidal fracture. Specific gravity: 2.35-2.60.
Formation & geological history
Forms as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth. Geological age varies widely depending on the volcanic deposit.
Uses & applications
Commonly used for ornamental objects, carved sculptures, holistic crystal healing, and historically for sharp tools such as arrowheads and blades.
Geological facts
Obsidian fractures with extremely sharp edges, often yielding cutting edges only a few nanometers thick, making it sharper than high-quality surgical steel.
Field identification & locations
Easily identified by its deep black color, glass-like luster, and characteristic conchoidal fracture. Found worldwide near recent volcanic activity.
