obsidian

Obsidian ( ) is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows. These flows have a high content of silica, giving them a high viscosity. The high viscosity inhibits the diffusion of atoms through the lava, which inhibits the first step (nucleation) in the formation of mineral crystals. T

AI overview

Obsidian is a naturally occurring volcanic glass created when lava from a volcano cools very quickly without forming crystals, resulting in a smooth, glassy igneous rock. Because the lava cools so rapidly, atoms cannot move around enough to form mineral crystals, which is what gives obsidian its distinctive glass-like properties.

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Key facts

Mineral.name: Obsidian
Mineral.category: Volcanic glass
Mineral.boxbgcolor: dddddd
Mineral.image: Lipari-Obsidienne (5).jpg
Mineral.color: usually black; sometimes green or brown; rarely yellow, orange, red or blue
Mineral.fracture: Conchoidal
Mineral.mohs: 5–6
Mineral.luster: Vitreous
Mineral.other: Texture: Smooth; glassy
Mineral.opticalprop: Translucent
Mineral.gravity: c. 2.4

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Wikidata facts

Image: A2613-Museum Geologi-Obsidian.jpg

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Commons category: Obsidian
Commons gallery: Obsidian
Mohs' hardness: 5.5

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Article

11 sections

Contents

Origin and properties
Occurrence
Prehistoric and historical use
Europe
Middle East and Asia
Americas
Oceania
Current use
See also
References
External links

Obsidian is hard, brittle, and amorphous; it therefore fractures with sharp edges. In the past, it was used to manufacture cutting and piercing tools, and it has been used experimentally as surgical scalpel blades.