Composition Of Granite And Basalt

The granite field comprises two sub fields.

Composition of granite and basalt.

Grant mason from the byu department of physics and astronomy discusses samples of granite and basalt rock. Granite cut and polished surface of granite magnified 1 5. In the upper part of qapf classification of plutonic rocks streckeisen 1976 the granite field is defined by the modal composition of quartz q 20 60 and the p p a ratio between 10 and 65. Rhyolite andesite and basalt form a series that varies in composition from felsic to mafic because of an increasing fraction of iron magnesium rich minerals that darkens the tone.

Granite is an intrusive igneous rock which is very hard crystalline and is visibly homogeneous in texture and forms by melting of continental rocks basalt forms when lava reaches the earth s surface near an active volcano. They can also be porphyritic with phenocrysts of olivine augite or plagioclase. Basalt is rich in iron and magnesium and is mainly composed of olivine pyroxene and plagioclase. It is the most common plutonic rock of the earth s crust forming by the cooling of magma silicate melt at depth.

In the simplified classification the intermediate intermediate toned aphanitic crystalline igneous rock is andesite. Granite coarse or medium grained intrusive igneous rock that is rich in quartz and feldspar. Among other differences the nature of these rocks reveals that basalt is basic in nature whereas granite is acidic in nature. This composition is as follows.

The temperature of lava is between 1100 to 1250 c when it gets to the surface. Most specimens are compact fine grained and glassy. 70 18 silicon dioxide sio2 14 47 aluminum oxide al2o3 4 11 potassium oxide k2o 3 48 sodium oxide na2o 1 99 calcium oxide cao 1 78 iron ii oxide feo 1 57 iron iii oxide 0 88 magnesium oxide mgo 0 84 water h2o 0 39 titanium dioxide tio2 0 19 diphosphorus pentoxide p2o5 and 0 12 manganese oxide mno. Of the two basalt is darker and consists of fine grained minerals such as magnesium and iron while granite is lighter and consist of feldspar and quartz.

Basalt is volcanic or extrusive forming at the surface while granite is plutonic or intrusive forming beneath the surface.