Obsidian. Lump of the volcanic rock obsidian. Obsidian is formed when volcanic lava is rapidly cooled on contact with water. The rock is mainly composed of silicon dioxide with impurities,such as iron,which give its black colour. Obsidian was used by Neolithic people to make tools because it leaves sharp edges when fractured | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / Martin, Doug |
Taille de l’image : | 4538 px × 3000 px |
Model Release : | Non requis |
Property Release : | Non requis |
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