Composition Of Granite And Basalt

Granite cut and polished surface of granite magnified 1 5.

Composition of granite and basalt. Basalt is volcanic or extrusive forming at the surface while granite is plutonic or intrusive forming beneath the surface. Among other differences the nature of these rocks reveals that basalt is basic in nature whereas granite is acidic in nature. Basalt is rich in iron and magnesium and is mainly composed of olivine pyroxene and plagioclase. Holes left by gas bubbles can give basalt a coarsely porous texture.

They can also be porphyritic with phenocrysts of olivine augite or plagioclase. Most specimens are compact fine grained and glassy. 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. 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.

Granite coarse or medium grained intrusive igneous rock that is rich in quartz and feldspar. This composition is as follows. 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. It is the most common plutonic rock of the earth s crust forming by the cooling of magma silicate melt at depth.

The granite field comprises two sub fields. In the simplified classification the intermediate intermediate toned aphanitic crystalline igneous rock is andesite. 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. Grant mason from the byu department of physics and astronomy discusses samples of granite and basalt rock.

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.