Materials of Construction 1.1 STONES Rocks from which stones are obtained may be classified in the following three ways: 1. Geological classification 2. Physical classification 3. Chemical classification. 1. Geological classification On the process of formation, rocks are classified as igneous rocks, sedimentary rocks and metamorphic rocks. (a) Igneous Rocks: These are the rocks formed by cooling of magma. These rocks are strong and durable. They are further classified as: Volcanic rocks: Cooling of magma at earth's surface - extremely fine grained and glossy. Examples: Basalt and trap. Hypahyssal rocks: Cooling of magma at shallow depth fine grained crystallized structure. Examples: Quartz, dolerite and gneiss. Plutonic rocks: Cooling of magma at considerable depth very strong and crystalline structure. Examples: Granite and dolerite. (b) Sedime ntary Rocks: Disintegrated rock material is carried by flowing water and deposited elsewhere. Year after year new layers of materials are...