The
familiar stone types that are used today are identified
through four categories: sedimentary, metamorphic,
igneous stone, and man-made.
I. 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.
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 limestone's can be polished.
Common colors are black, gray, 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.
Fossil stone: 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.
II. 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.
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)
1. Dolomite: If it has more than 40% magnesium
carbonate.
2. Magnesian: If it has between 5% and
40% magnesium carbonate.
3. 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.
III. 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.
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.
IV. 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.
