What kind of minerals are in granite

It is a granitic rock, but not true granite because the feldspar it contains is sodic plagioclase, not alkali feldspar. Width of sample from Norway is 10 cm. Syenite may be similar to granite, but it does not contain enough quartz. This sample is quartz alkali feldspar syenite from Estonia.

Width of sample 8 cm. Granite is a coarse-grained igneous rock with average grain size ranging from 1 to 25 millimeters 1. These rocks crystallize from a very slowly cooling magma within the crust where they are well insulated. Time gives crystals a chance to grow. Volcanic rocks with a similar composition exist as well. These are known as rhyolite volcanic equivalent of granite and dacite similar in composition to plagioclase-rich granitoids.

The groundmass of these rocks is very fine-grained although they frequently contain phenocrysts larger crystals that were already formed before the extrusion to the surface embedded in the finer matrix. Granite that crystallized in a narrow dike may be fine-grained because the heat was rapidly lost to the adjacent rocks.

Such granite is known as aplite. Sometimes granite is very coarse-grained. That too happens usually close to the margins of a granitic pluton, but the coarseness is mostly a result of volatiles in the magma which greatly reduce its viscosity and therefore enhance crystal growth.

These coarse-grained granites are known as pegmatites. It has often roughly uniformly sized crystals which show no preferred orientation but that is not always the case.

Some granites just like rhyolites contain phenocrysts — crystals that are clearly bigger than the material surrounding it. These phenocrysts are usually feldspar crystals. The difference between granite and rhyolite is that in granite even the finer material is visibly crystalline, but in rhyolite the individual crystals within the groundmass are not visible to the naked eye. Elongated minerals may have a preferred orientation.

Sometimes so much that it is no longer clear whether it is a granite or gneiss. Some granites have special textures like rims of one mineral around the other. Rapakivi granite is a notable example. Typical granite has visible mineral grains without any orientation. Orange mineral is alkali feldspar, gray is quartz. Picture taken in Norway. Width of view 20 cm.

It may have a preferred orientation. Note how most of the biotite flakes are aligned sub-parallel to each-other. Width of sample 15 cm. Aplite in the lower half is much finer than granite above it. Their composition seems to be the same. There are larger phenocrysts of quartz and feldspar within the granite. Width of sample 12 cm. Gneiss and granite may be the same compositionally, but elongated mineral grains are strongly oriented and segregated in gneiss.

The sample of gneiss is from Karelia, Russia. Width of sample 11 cm. Rhyolite and dacite are extrusive versions of granitic rocks. Their groundmass is very fine-grained, but they often contain phenocrysts, mostly feldspars. The sample from Scotland is 8 cm in width. Rapakivi texture plagioclase rims around ovoidal phenocrysts of alkali feldspar in granite.

Width of sample 17 cm. Graphic texture quartz intergrowth in feldspar that resembles runic script is common in pegmatites. Quartz crystals are uniformly scattered in the feldspar crystals and not randomly oriented. These crystals grew simultaneously with alkali feldspar host and they are optically continuous one crystal.

Evje, Norway. Width of sample 9 cm. A contact between gneiss granodioritic with migmatitic granite veins and granite pegmatite. Because it can be smoothed to a very high polish, granite has found extensive use in memorials, headstones, monuments, carved decorations on buildings, statues and the like. Approximately 1. Skip to content Return to Minerals Database. Type Rock. Related topics: Mica. Volcano Coloring Page. Pink colored granite is a result of an abundance of potassium feldspar within the granite.

However, in a granite like the one above the primary mineral is potassium feldspar. The above granite appears to have equal parts quartz, feldspar, and amphibole, making a speckled black and white granite. This is one of the most common types of granite and one that is most commonly seen used for granite countertops.

Red granite is a variation of pink potassium feldspar abundant granite, where the k-feldspar takes on a redder than pinker color. Also, you can get red coloring from iron oxide in hematite grains or inclusion within feldspar, essentially the same process that makes rusted metal ruby red colored.

You may find advertisements for blue granite countertops but this is also almost certainly not granite. One potential is that the rock is actually Larvikite , an igneous variety of monzonite and sometimes referred to as "blue granite" despite it not being granite.

Another common alternative is Anorthosite, a rock that contains abundant blue labradorite and is sometimes sold as blue granite. When advertised as green granite, often times the stone is actually a green variety of marble, which gains its green coloration due to inclusions of serpentine.

It could also be a green variation of soapstone, mislabeled as granite. Granites are not abundant in green colored minerals, but there are a variety of different rock types that do contain green minerals in abundance. One very unusual way to get a green coloration is the inclusion of amazonite , a green variety of feldspar. Lastly, we'll go through some of the most common types of granite and what gives them the color they have inherited. Granite is the rock most often quarried as a "dimension stone" a natural rock material that will be cut into blocks or slabs of specific length, width, and thickness.

Granite is hard enough to resist abrasion, strong enough to bear significant weight, inert enough to resist weathering, and it accepts a brilliant polish. These characteristics make it a very desirable and useful dimension stone. Most of the granite dimension stone produced in the United States comes from high-quality deposits in five states: Massachusetts, Georgia, New Hampshire, South Dakota, and Idaho.

Granite has been used for thousands of years in both interior and exterior applications. Rough-cut and polished granite is used in buildings, bridges, paving, monuments, and many other exterior projects. Indoors, polished granite slabs and tiles are used as countertops, floor tiles, stair treads, and many other practical and decorative features.

High price often reduces the popularity of a construction material. Granite often costs significantly more than man-made materials. However, granite is frequently selected because it is a prestige material, used in projects to produce impressions of elegance, durability, and lasting quality.

Granite is also used as a crushed stone or aggregate. In this form it is used as a base material at construction sites, as an aggregate in road construction, railroad ballast, foundations, and anywhere that a crushed stone is useful as fill.

What is Granite Used For? Article by: Hobart M. Did You Know? A Hand Lens is an important tool for learning about rocks. The minerals in a rock must often be identified to determine the rock's name. Azurite Granite , also called "K2 granite," is often cut into gems. People enjoy its blue and white colors.

Find Other Topics on Geology. Maps Volcanoes World Maps. What Is Granite? Related: Explore the many uses of granite! Rock, Mineral and Fossil Collections. Hardness Picks. Flint, Chert, and Jasper. Tumbled Stones. Fluorescent Minerals. Lapis Lazuli. Rocks: Galleries of igneous, sedimentary and metamorphic rock photos with descriptions. Minerals: Information about ore minerals, gem materials and rock-forming minerals. Volcanoes: Articles about volcanoes, volcanic hazards and eruptions past and present.