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Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth. Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) induces a high viscosity and polymerization degree of the lava.

Rose Quartz Geode Jewelry Supply - Druzy Stone Cabochon - Sparkling, Shimmering Crystal Center - Unique, DIY Jewelry Designs and Collectible

Rose Quartz Geode - This shows how beautiful the earth is on the outside and just as beautiful under it as well. I love these special rocks.

Gemmy pink Fluorite nestled between lustrous Pyrite, from Huanzala Mine, Hualanca District, Huanuco Department, Peru

A pyroclastic flow (also known scientifically as a pyroclastic density current) is a fast-moving current of hot gas and rock (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph).