Minerals

   A mineral is usually a natural inorganic substance having a definite chemical composition and a characteristic atomic structure. Though the term mineral is applied only to natural inorganic substances, the coal and petroleum are included under minerals, even though they are of organic origin. On the basis of its usefulness, all the minerals can be grouped into economic minerals and rock forming minerals. Silicates are the most important rock forming minerals. Accordingly the major silicate  families such as silica group, feldspar group, mica group and garnet group of minerals have been displayed.

    Minerals may be identified by their physical, chemical and optical properties. Above all minerals are the backbone of our modern industries.

   Smoky quartz is a smoky brown variety of quartz. Its colour is probably due to some organic compound. It is used as a semi-precious stone.

Chalcedony

     Chalcedony is a crypto-crystalline variety of quartz having a waxy lustre. Its surface is smooth and it breaks with a typical concoidal  fracture. It occurs in a variety of colours.

Rock Crystal

   Rock crystal is a colourless transparent variety of quartz. It is used as a semi-precious stone and in the manufacture of lenses, optical instruments and quartz crystal oscillators.

       Carnelian is a red to reddish brown variety of chalcedony. Its colour is due to the presence of iron. It is a semi-precious stone.  The Taj at Agra is studded with this type of stone.