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Type: Open-Ended
Category: Minerals
Level: Grade 7
Author: krlew
Last Modified: 11 years ago

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Minerals Question

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Grade 7 Minerals

Gems and Minerals

There are about 4,000 types of minerals on Earth. Of these, only about 15 are
used to make gems. Gems are minerals that may have been cut and polished to
make them sparkle.

The diamond is the hardest natural substance we know. Diamonds form deep
under ground at very high temperatures and pressure conditions caused by the
overlying thick layers of rock that squeeze the carbon atoms into a tight, strong
crystal.

Diamonds might grow under these conditions for 1 billion to 3 billion years and
therefore are considered the oldest gemstone. Only about 20 percent of diamonds
are made into jewels. Because they are so hard, most diamonds are used to make
tools such as dental drills and metal cutters.

Explain why hardness is a valuable property of some minerals.