Types of Stone

The familiar stone types that are used today are identified through 4 categories:

1. SEDIMENTARY
2. METAMORPHIC
3. IGNEOUS STONE
4. MAN-MADE.
   

SEDIMENTARY stone came from organic elements such as glaciers, rivers, wind, oceans, and plants. Tiny sedimentary pieces broke off from these elements and accumulated to form rock beds. They were bonded through millions of years of heat and pressure. Types of sedimentary stone:

LIMESTONE
Mainly consists of calcite. It does not show much graining or crystalline structure. It has a smooth granular surface. Varies in hardness. Some dense limestones can be polished. Common colors are black, grey, white, yellow or brown. It is more likely to stain than marble. Limestone is known to contain lime from sea water.
SANDSTONE
Is a very durable formation of quartz grains (sand). Usually formed in light brown or red colors. Categorized by the most popular sandstone bonding agents such as silica, calcium, clay, and iron oxide.
SOAPSTONE
A very soft stone made of a variety of talc. It is a dense mineral that wears well and is often resistant to stains.
FOSSILSTONE
Considered a limestone that contains natural fossils such as sea shells and plants.
TRAVERTINE
Usually a cream or reddish color. It is formed through the accumulation of calcite from hot springs. It contains lots of holes that were formed from water flowing through the stone. These holes are often filled with synthetic resins or cements. Requires lots of maintenance if the holes are not filled. Classified as a limestone and a marble.

METAMORPHIC stone originates from a natural change from one type of stone to another type through the mixture of heat, pressure, and minerals. The change may be a development of a crystalline formation, a texture change, or a color change. Types of metamorphic stone:

MARBLE
A recrystallized limestone that formed when the limestone softened from heat and pressure and recrystallized into marble where mineral changes occurred. The main consistency is calcium and dolomite. Ranges in many colors and is usually heavily veined and shows lots of grains. Hardness rates from 2.5 to 5 on the MOH Scale.
Marble is classified into three categories: (Stone World)
Dolomite: If it has more than 40% magnesium carbonate.
Magnesian: If it has between 5% and 40% magnesium carbonate.
Calcite: If it has less than 5% magnesium carbonate.
SLATE
A fine grained metamorphic stone that formed from clay, sedimentary rock shale, and sometimes quartz. Very thin and can break easily. Usually black, grey, or green.
SERPENTINE
Identified by its marks which look like the skin of a serpent. Most popular colors are green and brown. Hardness rates from 2.5 to 4 on the MOH Scale. Contains serpentine minerals has lots of magnesium, and has an igneous origin. Does not always react well to recrystallization or diamond polishing.

IGNEOUS stones are mainly formed through volcanic material such as magma. Underneath the Earths surface, liquid magma cooled and solidified. Mineral gases and liquids penetrated into the stone and created new crystalline formations with various colors. Types of igneous stone:

GRANITE
Primarily made of Quartz (35%), Feldspar (45%) and Potassium. Usually has darker colors. Contains very little calcite, if any. Provides a heavy crystalline and granular appearance with mineral grains. It is very hard material and easier to maintain than marble. Yet, it is still porous and will stain. There are different types of granite depending on the percentage mix of quartz, mica and feldspar. Black granite is known as an Anorthosite. It contains very little quartz and feldspar and has a different composition than true granite.

MAN-MADE Stones are derived of unnatural mixtures such resin or cement with the additive of stone chips. Types of Man-Made stone:

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