TYPES OF STONE

The types of stones that we use may be classified into four big categories: SEDIMENTARY, METAMORPHIC, IGNEOUS and MADE BY MEN.


SEDIMENTARY

These rocks are the result of the sedimentation of organic particles from glaciers, rivers, winds, oceans and plants that amalgamated after millions of years of heat and pressure. Within this category we have:

	LIMESTONE:	Limestone is a sedimentary rock consisting mainly of calcite. It has a smooth surface and a very fine graining originated from lime, although it doesn't feature a definite crystal structure. Its hardness differs, and some kinds of limestone are especially dense and may be polished. It is a delicate material and more malleable than marble. It comes in black, gray, white, yellow and brown.
	SANDSTONE:	Sandstone is a sedimentary rock with a very hard formation of grains and quartz (sand). It usually consists of silica, calcium, clay and iron oxide and comes in light brown or red colors.
	TRAVERTINE:	Travertine is a sedimentary rock that usually comes in creamy or reddish colors and is formed by the precipitation of calcite found in hot springs. This material exhibits holes that originated from water running through the stone. These holes are usually filled in with synthetic resins or cements to allow for easier maintenance. It may be classified as Limestone and Marble.

METAMORPHIC

Metamorphic rocks originated from a natural alteration from one stone to another under the influence of heat, pressure and minerals. This change may be in the crystalline structure or a change in texture and color.

	Marble:	Marble is re-crystallized limestone which was created when limestone softened by the means of heat and pressure and suffered a mineral alteration. It consists mainly of calcite and dolomite and has a wide range of colors, veins and granulation. Its hardness ranges from 2.5 to 5 in the MOH Scale.
	SLATE:	Slate is a metamorphic rock formed by fine grains of clay and sedimentary materials. Green stones contain some quartz. Common colors are black, gray and green.
	SERPENTINE:	The serpentine got its name due to marks similar to the snake's skin. The most popular colors are green and brown. Its hardness ranges from 2.5 to 4 MOH. It contains magnesium and is of igneous origin. It does not always react well to re-crystallization or to polishing.

IGNEOUS

These stones are basically formed by volcanic material such as molten rock. Liquid magma cooled down and solidified beneath the surface of the Earth. Mineral gases and liquids penetrated the stone and created new crystalline forms in various colors.

GRANITE:

Granite is an igneous stone, mainly composed of quartz (35%), feldspar (45%) and potassium, with a lesser amount of calcium. It has a very crystallized structure and many mineral grains in different colors. Although it is much harder than marble, it may stain, because it is porous. Granite is much more resistant than marble.

MAN-MADE

MAN-MADE  Stones are derived of unnatural mixtures such resin or cement with the additive of stone chips.
TERRAZZO:  Marble and granite chips embedded in a cement composition.
AGGLOMERATE or CONGLOMERATE:  Marble chips embedded in a colored resin composition.
CULTURED or FAUX MARBLE:  A mix of resins that are painted or mixed with a paint to look like marble.