The Colors Of Granite Depend On The Mineral Grain Size

Using your knowledge of this information for the igneous rocks listed place the rock.

The colors of granite depend on the mineral grain size.

If the molten rock was abundant in potassium feldspar the granite is more likely to take on a salmon pink color. But a rapidly cooled volcanic rock with the same composition as the granite could be entirely. 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. Peridotite basalt gabbro diorite rhyolite.

The grain size is coarse enough to allow recognition of the major minerals. It is about two inches across. Of course diorite and andesite have the same mineral content and occur in the same areas. Slow cooling of diorite results into coarse grain size due to large crystals formation with more ion transport.

For example a granite consists of lots of quartz and feldspar and is generally light colored. On the other hand if the molten rock is abundant in quartz and minerals that make. Not a problem for rapid cooling of plutons. Trace minerals such as mica and amphiboles also affect the color and composition.

The pink grains are orthoclase feldspar and the clear to smoky grains are quartz or muscovite. Quartz is milky white feldspar is white potassium feldspar is pink biotite is black or brown muscovite is yellow and amphibole is green. When that happens the granite is called a pegmatite. The minerals found in granite are typically light colored and may vary depending on which minerals are prevalent.

Numerous other minerals can be present in granite. The difference is grain size and cooling rate during the rock formation process. The black grains can be biotite or hornblende. Under certain conditions the mineral grains can grow very large.

Granite and gabbro are examples of. Coarse grain varieties with mineral grains large enough to see without a magnifying glass are called phaneritic. Ferromagnesium minerals are dark colored. 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.