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Obsidian

Igneous Rocks

A naturally occurring volcanic glass, an igneous rock formed when felsic lava cools so rapidly that mineral crystals barely form. The high silica content of the rhyolitic flows it comes from makes the lava so viscous that atoms cannot arrange into crystals, and rapid cooling finishes the job, leaving a natural glass whose conchoidal fracture gave prehistory its sharpest cutting edges. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/

Facts
Kind
Rock 3
Formation Class
Igneous, extrusive (volcanic glass formed when lava cools rapidly with minimal crystal growth) 3
Chemical Formula
Obsidian is a volcanic glass consisting mainly of SiO2 (silicon dioxide), usually 70 percent by weight or more. 3
Hardness (Mohs)
5.5 1
Classification
Classification
Igneous Rock 1
Use
Industrial and Abrasive 2
Wikipedia 'Obsidian' states this use (or use-bearing statement); earth5 pass.
Connections

Caused By

Volcanism, Processes

Formed when lava extruded from a volcano cools rapidly with minimal crystal growth.

Source Obsidian (Wikipedia)

Classified As

Igneous Rocks, Subcategories

In Discipline

Geology, Disciplines
Source Obsidian (Wikipedia)
Sources
1. Obsidian (Geology.com)
  • Uses of Obsidian in Jewelry section
    It has a hardness of about 5.5 which makes it easy to scratch.
  • Lead section
    Maps Volcanoes World Map World Records Map Collections Africa Maps Antarctica Map Arctic Map Asia Maps Australia Map Canada Maps Caribbean Maps Central America Maps Europe Maps North America Maps South America Maps United States Maps World Maps Advertising Home » Rocks » Igneous Rocks » Obsidian Obsidian What is Obsidian, How Does it Form, and What is it Used For?
View the Source
2. Wikidata: Obsidian
Wikidata Q53754
3. Obsidian (Wikipedia)
Wikimedia Foundation
  • Lead section
    Obsidian (, əb-SID-ee-ən ob-) is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth.
  • Origin and properties section
    Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% by weight or more
View the Source
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