Wednesday, 18 March 2015



Diorite is an intrusive igneous rock and is coarse grained because of the greater time for settling. It is between granite and gabbro and is similar to the fine grained extrusive rock, andesite. Diorite is composed mainly of plagioclase feldspar with amphibole and pyroxene minerals. The black minerals in diorite are hornblende and the whote mineral is plagioclase feldspar. The diorite has no or very little amount of quartz unlike granite. The sodic plagioclase minerals of the diorite gives it a high relief look. 

Diorite classification

The classification of diorite can be by the minerals constituent of the rock as, with a little quartz it becomes quartz diorite and with more quartz it become tonalite. With more alkali feldspar it becomes monzonite and when both minerals are abundant then the diorite becomes granodiorite. 

Diorite appearance

Diorite has white and black minerals which gives it salt and pepper appearance. The identification of diorite in the field can be by using a hand lens to look for plagioclase minerals intersecting at oblique angles.  


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