Question

list igneous rock

Answer 1

Igneous rocks are formed from the solidification of molten rock material.

There are two basic types :- a) Intrusive igenous rock

b) Extrusive igenous rock

a) Intrusive igenous rock :

crystallize below earth's surface,and the slow cooling that occurs there allows large crystals to form.

examples:- diorite , gabbro, granite, pegmatite , and peridotite .

b) Extrusive igenous rock :

erupt onto the surface, where they cool quickly to form small crystals. some cool so quickly that they form an amorphous glass.

examples :- andesite , basalt , dacite, obsidian , pumice , rhyolite , scoria , and tuff.

Brief descriptions of some common igenous rock types

Diorite : -

Diorite is a coarse grained intrusive igenous rock that cintains a mixture of feldspar,,pyroxene,hornblende, and sometimes quartz.

Gabbro :-

Gabbro is a coarse grained dark colored intrusive igenous rock that contains feldspar,pryroxene and sometimes olivine.

Granite :-

Granite is a coarse grained light colored intrusive igenous rock that contains mainly quartz,feldspar and mica minerals.

Pegmatite :-

Pegmatite is a light colored extremely coarse grained intrusive igenous rock.It forms near the margins of a magma chamber during the final phases of magma chamber crystallization.It often contains rare minerala that are not found in other parts of the magma chamber.

Peridotite : -

Peridotite is a coarse grained intrusive igneous rock that is composed almost entirely of olivine.It may contain small amounts of amphibole, feldspar, quartz, or pyroxene.

Andesite :-

Andesite is a fine grained extrusive igenous rock composed mainly of plagioclase with other minerals such as horblende, pyroxene, and biotite.

Dacite :-

Dacite is a fine grained extrusive igenous rock that is usually light in colour. it has a compostion that is intermediate between rhyolite and andesite.

Basalt :-

Basalt is a fine grianed dark colored extrusive igenous rock composed mainly of plagioclase and pyroxene.

Obsidian :-

Obsidian is a dark colored volcanic glass that forms from the very rapid cooling of molten rock material.It cools so rapidly that crystals do not form.

Pumice :-

Pumice is a light colored vesicular igenous rock. it forms through very rapid solidification of a melt. The vesicular texture is a result of gas trapped in the melt at the time of solidification.

Fire Opal :-

Fire Opal is sometimes found filling cavities in rhyolite.Long after the rhyolite has cooled silica rich ground water moves through the rock, sometimes depositing germs like opal,red beryl,topaz,jasper or agate in the cavities of the rock. This is one of many excellent geological photographs generously shared through a creative commons license by didier descouens.

Rhyolite :-

Rhyolite is a light colored fine grained extrusive igneous rock that typically contains quartz and feldspar minerals.

Welded Tuff :-

Welded Tuff is a rock that is composed of materials that were ejected from volcano,fell to earth and then lithified into rock ..It is usually composed mainly of volcanic ash and sometimes contains larger size particles such as cinders.

Scoria :-

Scoria is a dark colored vesicular extrusive igenous rock. The vesicles are a result of trapped gas within the melt at the time of solidification.It often forms as a frothy crust on the top of a lava flow or as material ejected from a volcanic vent and solidifying while airborne.