Discovering minerals

Minerals are naturally occurring inorganic substances that have specific chemical compositions and physical properties of their own. They are solid in nature and have definite crystalline structures, and are an outcome of geological processes. They can be formed by cooling of hot melting material, evaporation, or by precipitation. Their composition ranges from pure elements to complex silicates. Since oxygen and silicon are the most abundantly available elements, silicates are the most widespread minerals on earth.

• • •

Which chemical is used in the lead of a pencil?

The chemical lead was used by the Romans as lead rods to write on papyrus. These rods left a grey mark just like graphite. Hence, graphite was believed to be a type of lead. In 1564 a graphite deposit was discovered in England, which led to its widespread use for writing. The lead used in pencils are not actually the chemical lead but graphite and clay. An average pencil can write about 45,000 words, or a line about 35 miles (56 km) long.

• • •