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Obsidian



What is Obsidian?



Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.

obsidian
Obsidian: The specimen shown is about two inches (five centimeters) across.


Igneous Rocks
Metamorphic Rocks
Sedimentary Rocks
Sliding Rocks of Racetrack Playa
Spectacular Yosemite Rockfall
Free Guide to Rock Tumbling
Coal Through a Microscope
Uses of Granite
Petroglyphs and Pictographs
Rocks and Minerals


The rock photos above were taken by Ann Bryant and are copyright by Geology.com.
 
Igneous Rocks
Andesite
Andesite		   Basalt
Basalt

Quartz Diorite
Diorite		   Gabbro
Gabbro

Granite
Granite		   Obsidian
Obsidian

Pegmatite
Pegmatite		   Peridotite
Peridotite

Pumice
Pumice		   Rhyolite
Rhyolite

Scoria
Scoria		   Welded Tuff
Tuff




A Guide to Rock Tumbling
Rock Tumblers: Step-by-step guide to tumble-polishing rocks into gemstones. And an article: How to select a tumbler.

Igneous rock
Igneous Rock Photo Gallery: A collection of igneous rock pictures and short descriptions.

Kilauea lava flows
Photos of Kilauea Lava: Spectacular USGS photos of lava flows pouring into the Pacific.

Volcano news and information
Volcanoes! A page that links to all of our volcano articles and to the best volcano information that we could find.

Racetrack Playa
Sliding Rocks - Racetrack Playa: How these rocks slide across a dry lake bed is a mystery. Photo © iStockphoto / Stephan Hoerold.

Mount Vesuvius images and information
Mount Vesuvius: An interesting article with photos and maps that describes the volcano's eruption history, geologic hazards, plate tectonics and more.

gneiss
Metamorphic Rocks: Photos and facts about foliated and non-foliated metamorphic rocks.

conglomerate
Sedimentary Rocks: Photos and facts about clastic, chemical and organic sedimentary rocks.

Rock tumbler


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