Rose quartz is a pink variety of quartz and it is used as a semi-precious stone. It is less common in occurrence when  compared to the other varieties of quartz.

    Opal is an amorphous variety of quartz with varying amounts of water. It occurs in a variety of colours and gives a white streak. Its hardness varies from 5.5 to 6.5 and its specific gravity ranges from 1.9 to 2.2. It breaks with a marked concoidal fracture.

   Plasma is a dark to light green variety of chalcedony and is sub-translucent or slightly translucent. Its colour is due to the presence of chlorite. It is used as an ornamental stone.

      Chert or hornstone is an impure form of  flint and is usually brittle.

Yellow Quartz

     The quartz is the member of the silica group of minerals. Its hardness is seven. It is yellow in colour. Hence it is called as yellow quartz. The quartz is used in the manufacture of  glass, porcelain and refractories.