Key notes for class 12 Chemistry chapter 06 General Principles and Processes of Isolation of Elements. it includes revision notes such as The naturally occurring chemical substances in the earth’s crust which are obtained by mining are known as minerals. Metals may or may not be extracted profitably from them. The rocky materials which contain sufficient quantity of mineral so that the metal can be extracted profitably or economically are known as ores. The entire scientific and technological process used for isolation of the metal from its ores is known as metallurgy.