Granodiorite Rock - A Complete Guide

Granodiorite is less known and used igneous rock falling in intrusive type. It is akin to granite in look but containing a high percentage of plagioclase (K & Ca-rich) feldspar so looks off-white in color.

Mineralogy of Granodiorite

It contains less than 20% Quartz. Other minerals are plagioclase, which is always greater than 2/3 of total feldspar. The plagioclase is with lesser orthoclase, Biotite, and amphibole (hornblende). It has Silica (SiO 2) content – 63%-69%.

• It is felsic to intermediate in mineral content.
• It is intrusive igneous rock.
• It has a large amount of sodium and calcium in plagioclase.
• It has potassium feldspar, some quartz, and a bit of muscovite mica.
• Biotite & amphiboles give it a two-toned but darker look.
• Mica found in hexagonal crystals while hornblende found in needle-like crystals.
• Magnetite, limonite, ulvospinel like oxide minerals, as well as some sulfide minerals are present in it. 

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