Rocks

abstract from " A Guide to good quality control practices on asphalt production and construction"

Rocks are classified relative to their geological origins and these are termed Igneous, Sedimentary and metamorphic

1. Igneous Rocks

formed from hot liquid or magma, cooling either above or beneath the earth's surface.
examples are Grannite & basalt

2. Sedimentary Rocks

The action of wind or water on a rocks surface results in the formation of smaller particles. These particles are deposited on river or sea beds or depressions in the earth's surface. This sediment accumulates and is buried. Compaction and cementation over the years removes the air and water to form sedimentary rocks.
Typical example is Limestone

3. Metamorphic rocks

Heat, pressure and chemical substances deep beneath the earth's surface act on existing igneous and sedimentary rocks to form a new type called metamorphic rocks, example marble