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FORTHCOMING EVENTS

   

The 'Virtual'

Festival of Geology 2020

Saturday 7th and Sunday 8th November 2020

Save the dates!​​​​​​​

  

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OBSIDIAN - Western USA

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Home > MINERALS > UNUSUAL ROCKS AND MINERALS - WEIRD AND WONDERFUL !

 
OBSIDIAN

Western USA
 
Obsidian is a natural volcanic glass, formed when lava from a volcano cools extremely quickly leaving no time for crystals to grow.  It is the same chemical composition as granite but granite has cooled very slowly deep underground forming large crystals. 

The lava that produces obsidian is usually sticky and highly viscous, resulting in explosively violent volcanic eruptions. 

This is a dense, black example with impressive conchoidal fracture surfaces.
 
Caution: Just like man-made glass, broken pieces of obsidian have very sharp edges.

Click on a picture for a larger image


Size:  11.5 x 8.5 x 6 centimetres
Weight:  663 grams

PRICE: £18.00