mysqlClass Error 9 in file extras/autoload.inc.php, line 72:
Error #8192: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead
IGNEOUS ROCKS

IGNEOUS ROCKS

SRI Petrography ID: 3

granite from Schärding
Upper Austria

Names

[de] MAGMATISCHE GESTEINE
[en] IGNEOUS ROCKS

Description

Igneous rocks comprise one of the three principal classes of rocks (the others being metamorphic and sedimentary rocks). Whereas most metamorphic rocks show typical metamorphic texture (banding, foliation, layering) and sedimentary rocks mostly show sedimentary textures (banking, bedding), igneous rocks (plutonites) usually show no orientation of their grains.
An igneous rock is a rock of various appearance, either crystalline or glassy or noncrystalline, formed by the cooling and solidification of magma (melt of rocks). Most igneous rocks consist of minerals like quartz, feldspar, pyroxene, amphibole, mica, apatite, olivine, nepheline or leucite. They are either of intrusive (plutonites) or extrusive (volcanites) origin.
Thus they can be classified also by their grainsize and texture visually:
coarse-grained (e.g. granites and gabbros)
fine grained (e.g. basalt)
glassy (e.g. obsidian)
porphyric
pyroclastic rocks (e.g. tuffs).


Color

variable

Grain Size

Coarse grained, fine grained, glassy, porphyric (depending on type)

Texture

variable, mostly no grain orientation, sometimes porphyric

Minerals

varyable, most common:
quartz, feldspar, pyroxene, amphibole, mica, apatite, olivine, nepheline or leucite

Occurences

all over the world

Classification

Narrower Terms

coarse-grained crystalline rocks

fine-grained crystalline rocks

glassy igneous rocks

porphyric (inequigranular) crystalline rocks

pyroclastic rocks