Basic Facts About Natural Stones

Basic Facts About Natural Stones

Natural stone is a common name of different types of stone which are naturally found and quarried throughout the world. All natural stones are unique as no geographical composition or forces are same on different parts of the world. This means that natural stone of the same type can also differ widely. Usually natural stones are characterized by the manner in which they have been formed by volcanoes, by tectonic folding, by rivers.
Geologists have divided natural stones into three major groups Igneous, Sedimentary and Metamorphic.

Igneous Stones:

This group of stones has been formed by solidification of molten material or magma both on the earth's surface and below it. Igneous stones greatly differ from each other depending on where they have been formed as rate of cooling is different at different levels of the earth's surface. Granite is an example of igneous stone used for building and monumental purposes.

Sedimentary Stones:

Sedimentary stones are formed by accumulation and deposition of fragmentary materials and deposition of organic remains over long periods, usually under water. The materials that form sedimentary stones may be brought by streams, glaciers, winds or even animals.

Sedimentary stones are classified into there 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, often quartz fragments derived from granites.

2. Organically formed sedimentary stones-

These stones are formed from the remains of living organisms such as corals or shell fish, whose fleshy parts have been decomposed, leaving behind the 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 other. Stone salts are derived from strata which, once formed the beds of seas or lakes. For example limestones are formed mainly from the shells and skeletons of dead marine organisms.

Metamorphic Stones:

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, basalt and slate are the most popular.