About Natural Stone
Natural stone is a common name of different types of stone which are found and quarried throughout the world. All natural stone is unique as no geographical composition or forces are the same in different locations around the world. This means that the same type of natural stone can also differ widely. Geologists have divided natural stones into three major groups Igneous,Sedimentary and Metamorphic.
This group of stones has been formed by solidification of molten material or magma both on the earth’s surface and below. Igneous stones greatly differ from each other depending on where they have been formed as rate of cooling is different on different levels of the earth’s surface. Granite is an example of igneous stone.
Sedimentary stones are formed by accumulation and deposition of fragmentary materials and organic remains over a long period of time usually under water. The materials that form sedimentary stones are produced by water sources such as lakes, rivers, glaciers, weather and even animal life.
Sedimentary stones are classified into three main categories in accordance with their origin and composition
1. Mechanically formed sedimentary stones-
These have been formed from the accumulation of materials derived from other rocks which have been cemented together. Sandstones are probably the most familiar sedimentary stone. They are made from sand grains and quartz fragments derived from granites.
2. Organically formed sedimentary stones-
These stones are formed from the fossilized remains of living organisms such as corals or shell fish, whose fleshy parts have been decomposed, leaving behind hard shells. Coral stone is one of the organically formed sedimentary stones.
3. Chemically formed sedimentary stones-
Such stones are precipitated chemically from solutions of one kind or another. Stone salts are derived from strata which once formed the beds of seas or lakes. Limestone is formed mainly from the shells and skeletons of dead marine organisms.
All stones whether igneous or sedimentary may become metamorphic (derived from Greek word Meta=change and Morph=a change in form) or changed stones under great heat or pressure. Their original character and appearance may be greatly altered by such natural forces, particularly during intense earth movements. In this manner clay may be metamorphosed into slate, limestone into marble and sandstone into quartzite.
For commercial purposes, natural stone is divided into several groups: granite, marble, limestone, travertine, basalt and slate are the most popular.