Answers

2016-03-13T19:06:24+05:30
Crystal is coal under high pressure. It;s expensive because it s rare and demand is high, supply is low.
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2016-03-13T19:12:38+05:30
Crystals are the other forms of carbon which are kept under high pressure to form as diamonds or etc..,
They are too costly because they are very expensive to prepare and they are very rarely occuring substances in the nature

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