The Colors Of Granite Depend On The Mineral Grain Size

Quartz is milky white feldspar is white potassium feldspar is pink biotite is black or brown muscovite is yellow and amphibole is green.

The colors of granite depend on the mineral grain size.

Slow cooling of diorite results into coarse grain size due to large crystals formation with more ion transport. It is about two inches across. The minerals found in granite are typically light colored and may vary depending on which minerals are prevalent. Not a problem for rapid cooling of plutons.

The black grains can be biotite or hornblende. The classification of igneous rocks depends on both grain size and silica composition. The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite. For example a granite consists of lots of quartz and feldspar and is generally light colored.

Coarse grain varieties with mineral grains large enough to see without a magnifying glass are called phaneritic. Ferromagnesium minerals are dark colored. On the other hand if the molten rock is abundant in quartz and minerals that make. The grain size is coarse enough to allow recognition of the major minerals.

But a rapidly cooled volcanic rock with the same composition as the granite could be entirely. The difference is grain size and cooling rate during the rock formation process. Grain size can vary greatly from extremely coarse grained rocks with crystals the size of your fist down to glassy material which cooled so quickly that there are no mineral grains at all. The overall color of granite depends largely on the kind of feldspar in the.

But color can be misleading when applied to rocks of the same composition but different grain size. Using your knowledge of this information for the igneous rocks listed place the rock. If the molten rock was abundant in potassium feldspar the granite is more likely to take on a salmon pink color. Of course diorite and andesite have the same mineral content and occur in the same areas.

Numerous other minerals can be present in granite. Peridotite basalt gabbro diorite rhyolite. The most common colors of granite are white pink yellow grey and black primarily because of its composition. The specimen above is a typical granite.

When that happens the granite is called a pegmatite. Trace minerals such as mica and amphiboles also affect the color and composition.