Black Minerals In Granite

Numerous other minerals can be present in granite.

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. The grain size is coarse enough to allow recognition of the major minerals. The specimen above is a typical granite. That light background color is punctuated by the darker accessory minerals.

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. White granite is a granite that is composed primarily of quartz milky white and feldspar opaque white minerals. The quartz and feldspar generally give granite a light color ranging from pinkish to white. Its three main minerals are feldspar quartz and mica which occur as silvery muscovite or dark biotite or both.

Crystals are common with striated faces shaped in octahedrons or dodecahedrons. Granite is high in quartz about 25 feldspar and mica. Color variation is a response to the percent of each mineral found in the sample. Look for a black streak and a strong attraction to a magnet.

It may be gray black or have a rusty coating. The black grains can be biotite or hornblende. It is about two inches across. Thus classic granite has a salt and pepper look.

The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite.