What are rocks?

Rocks are assemblence of one or more minerals. Therefore every Geologist must have learnt the compositions and identifications of minerals to be able to study rocks. The study of minerals is called mineralogy. There are approximately 4000 unique minerals(200 common minerals) that make up the 3 major kinds of rocks; sedimentary rocks, methamorphic rocks, and the igneous rocks.

Learning to identify minerals in class was a huge problem for me as I used to memorise the characteristics of certain minerals to identify them until i was thought to look at it in a broader manner, by categorizing those minerals into larger groups.

Minerals from Igneous Rocks make up almost 75% of the minerals in the Earth. There are only 7 groups of minerals under Igneous Rocks; Olivine, Quartz, Pyroxene, Plagioclase, Orthoclase, Biotite, and Amphibole. So if you pick up a rock and some one asks you to identify the minerals in it, most of the time if you guess one of these 7 groups of minerals, you will be right. So for all of you who read this, try memorising the names of these few minerals and you can then sound like a geologist.

The white mineral in the picture is known as Quartz which is mainly made up of only silicon and oxygen under certain amount of temperature and pressure. The green mineral in the picture is called Olivine (Fosterite in particular) which is made up of Magnesium, Silicon, and Oxygen.

Georgius Agricola (1580) is known as the 'Father of Mineralogy'. His books were used by many European mining companies to increase the efficiency of their outputs.