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obsidian specimens group a naturally occurring volcanic glass

£23.00 £18.00

SKU: OSG Categories: ,

Description

a group of 3 obsidian specimens offered at a special price

Specimendimension (cm)weight (g)
Snowflake obsidian8x8x7483
Apache Tear6x5.5x4.5158
Obsidian6x5x4104

This 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 minimal crystal growth. 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 polymerisation degree of the lava. The inhibition of atomic diffusion through this highly viscous and polymerised lava explains the lack of crystal growth. Obsidian is hard and brittle; it therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, and it has been used experimentally as surgical scalpel blades.

see Wikipedia

Additional information

Weight 745 g