Question

Rocks are grouped according to

Answer 1

Rocks are grouped according to their formation into three major groups – igneous, sedimentary, and metamorphic rocks

Explanation:

• Based on their formation, rocks are further sub-grouped as:

1. Igneous - Intrusive or extrusive
2. Sedimentary – Clastic, chemical, or biologic rocks
3. Metamorphic - Foliated and non-foliated

• Rocks are also grouped based on their properties like size, shape, texture, chemical composition, permeability, mineralogy, etc.

• Based on properties rocks are sub-grouped as:

1. Igneous rocks – coarse or fine-grained; glassy or obsidian; felsic or mafic.
2. Sedimentary rocks - conglomerate, sandstone, breccia, shale, siltstone, chalk, crystalline or fossiliferous limestone, gypsum, rock salt etc.
3. Metamorphic rocks - Gneiss, hornfels, mylonites, cataclasties, marble, etc.