On the basis of chemical and physical properties, minerals may be grouped under two main categories of metallics and non-metallics. Metallic minerals are the sources of metals. Iron ore, copper, gold produce metal and are included in this category. Non-metallic minerals are either organic in origin such as fossil fuels also known as mineral fuels which are derived from the buried animal and plant life such as coal and petroleum. Other type of non-metallic minerals are inorganic in origin such as mica, limestone and graphite, etc.