Black Minerals In Granite

The crystals in granite provide a variety of mixed colors feldspar pink or red mica dark brown or black quartz clear pink white or black and amphibole black.

Black minerals in granite.

The grain size is coarse enough to allow recognition of the major minerals. Color variation is a response to the percent of each mineral found in the sample. Granite is the most common intrusive rock in earth s continental crust it is familiar as a mottled pink white gray and black ornamental stone it is coarse to medium grained. Thus classic granite has a salt and pepper look.

Granite is high in quartz about 25 feldspar and mica. Magnetite or lodestone is a common accessory mineral in coarse grained igneous rocks and metamorphic rocks. The most common accessory minerals are the black mica biotite and the black amphibole hornblende. That light background color is punctuated by the darker accessory minerals.

The specimen above is a typical granite. The black grains can be biotite or hornblende. White granite is a granite that is composed primarily of quartz milky white and feldspar opaque white minerals. It may be gray black or have a rusty coating.

The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite. Numerous other minerals can be present in granite. It is about two inches across. The small black specks in the granite above are likely small amphibole grains.

Crystals are common with striated faces shaped in octahedrons or dodecahedrons.