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 | | Mankind used rocks, stones, bones and wood to form the earliest tools. It is from this that we get the term 'Stone Age' to describe the earliest part of human history. But early man clearly studied the different properties of the rocks, stones and materials available to make the best tools possible. Flint produces hard, sharp edges when chipped. So, early knives, spears and arrows used flint to deadly effect. Granite is hard-wearing, whereas sandstone is soft and less durable. Clay is easily shaped to make bowls and jugs or decorative items like beads. Some stones, like gem stones or precious stones, are valuable only for their beauty. But obsidian is that rare thing in nature – a stone that is both beautiful and extremely useful for many things. |
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Obsidian is a type of glass that volcanoes create when they erupt. The volcano melts minerals and rocks from deep underground and throws them up to the surface. Volcanoes create many different types of rock in this process. Of them all, however, obsidian is one of the most interesting. Like glass, obsidian is relatively light in weight and smooth to the touch. It also breaks to create extremely sharp edges. Smooth obsidian can reflect light like a mirror. On the other hand, like rock, obsidian is very hard and dark. The interesting thing about obsidian is that it lacks the crystalline structure of most rocks. This means obsidian blade edges can reach almost molecular thinness to make the finest cutting edges possible. This amazing property, combined with the natural glass-like beauty and hardness of the rock, makes obsidian a truly unique material when it comes to tool making. Pure obsidian is usually very dark and glass-like in appearance, though the colour varies depending on the presence of impurities. Iron and magnesium typically give obsidian a dark green to black colour. But some obsidian include beautiful white flakes, while others show the colours of the rainbow. These stones are called "snowflake" and "rainbow" obsidian respectively. Gem collectors love these particular types of obsidian the most.
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Glossary
Volcano (n)
a mountain that forces hot gas and rocks into the air through an opening at the top.
Unique (adj)
very special and unusual.
Gem (n)
a beautiful stone that is used to make jewellery. |
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Last Updated ( Thursday, 06 May 2010 10:02 )
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