The Colors Of Granite Depend On The Mineral Grain Size

Of course diorite and andesite have the same mineral content and occur in the same areas.

The colors of granite depend on the mineral grain size. Under certain conditions the mineral grains can grow very large. The difference is grain size and cooling rate during the rock formation process. The classification of igneous rocks depends on both grain size and silica composition. On the other hand if the molten rock is abundant in quartz and minerals that make.

Granite and gabbro are examples of. Trace minerals such as mica and amphiboles also affect the color and composition. Not a problem for rapid cooling of plutons. The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite.

But color can be misleading when applied to rocks of the same composition but different grain size. The specimen above is a typical granite. Coarse grain varieties with mineral grains large enough to see without a magnifying glass are called phaneritic. The most common colors of granite are white pink yellow grey and black primarily because of its composition.

The grain size is coarse enough to allow recognition of the major minerals. It is about two inches across. 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. Using your knowledge of this information for the igneous rocks listed place the rock.

The black grains can be biotite or hornblende. The overall color of granite depends largely on the kind of feldspar in the. One objection to the earth being only 6 000 years old as described in the bible is the claim that the coarse grained texture of granites shows they cooled slowly over millions of years. When that happens the granite is called a pegmatite.

Ferromagnesium minerals are dark colored. Quartz is milky white feldspar is white potassium feldspar is pink biotite is black or brown muscovite is yellow and amphibole is green. The minerals found in granite are typically light colored and may vary depending on which minerals are prevalent. Slow cooling of diorite results into coarse grain size due to large crystals formation with more ion transport.

But a rapidly cooled volcanic rock with the same composition as the granite could be entirely. For example a granite consists of lots of quartz and feldspar and is generally light colored.