what are the different groups of igneous, sedimentary and metamorphic rocks?

Answer 1

You have a vague question, are you asking for subdivsions of the three main types of rocks?

Igneous rocks can be divided into intrusive (granite, syenite, gabbro, etc.) and extrusive or volcanic (rhyolite, anddesite, basalt, etc.)

Sedimentary rocks can be divided into clastic (conglomerate, sandstone, shale) and chemical (gypsum, limestone).

Metamorphic rocks can be divided into metaigneous (formerly igneous such as orthogneiss) and metasedimentary (formerly sedimentary such as paragneiss, quartzite, and marble).

Hope that helps!

Answer 2

Igneous rocks are caused by volcanoes and lava. Obsidian would be a good example. Sedimentary rocks are caused by sediment (silt, dirt, and mud) being layered upon each other and then hardened by the pressure (limestone). Metamorphic rocks were sedimentary rocks that were placed under intense heat and pressure until the changed (marble).

Answer 3

There are many ways to group the rocks.
Igneous can be intrusive or extrusive depending on whether they reach the earths surface or not. The can also be classified by the amount of free quartz and other minerals into ultra-basic, basic, intermediate and acidic (most free quartz).
Within these there are many sub-groupings.

Sedimentary rocks are classified commonly by grain size;
arenaceous and argillaceous for sand muds and clays, but they can also be classifed by their chemical make-up.

Metamorphic rocks fall into two main groups; those formed by pressure (regional) metamorphism, and those made by heat (contact) metamorphism. Then they can be subgrouped according to what the rock was originally before being metamorphosed.