Black Minerals In Granite

White granite is a granite that is composed primarily of quartz milky white and feldspar opaque white minerals.

Black minerals in granite. The quartz and feldspar generally give granite a light color ranging from pinkish to white. Granite is high in quartz about 25 feldspar and mica. Crystals are common with striated faces shaped in octahedrons or dodecahedrons. It may be gray black or have a rusty coating.

Numerous other minerals can be present in granite. Look for a black streak and a strong attraction to a magnet. Thus classic granite has a salt and pepper look. 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.

The specimen above is a typical granite. The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite. The grain size is coarse enough to allow recognition of the major minerals. 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.

Magnetite or lodestone is a common accessory mineral in coarse grained igneous rocks and metamorphic rocks. That light background color is punctuated by the darker accessory minerals. Color variation is a response to the percent of each mineral found in the sample. The most common accessory minerals are the black mica biotite and the black amphibole hornblende.

It is about two inches across.