Stone is a natural solid formation of one or many minerals. There are
thousands of types of stone that have been quarried through the centuries.
Quarries are located all around the world. A majority of natural stone comes
from Italy, Spain, Turkey, United States, Mexico, China, Taiwan, India,
Greece, Canada, France, and Brazil.
The minerals in stone came from the same liquid and gas minerals that formed
the earth. The Earth developed as a massive body of gas and liquid minerals
that slowly cooled and condensed to a solid core. Through pressure, the
Earth's crust began to form and heavy minerals were forced down to the core
of the Earth where they were trapped. As the crust got thicker, it squeezed
around the inner core which created intense pressure and heat from within
the Earth. Crystals and other solid forms began to grow from the mineral
vapors that were being released. As the Earth's crust began to expand and
erode, heat and pressure pushed the solid minerals up to the Earth's surface
which formed colossal rock beds. It took up to one-hundred million years to
form some of these beds. Many of the beds are now used as quarries where the
stone is mined.
Most of these minerals can be identified by their color, hardness, and
crystal formation. Crystals come in a variety of shapes and sizes. The wide
array of these minerals are often difficult to identify. Many stones look
very similar to each other; however, they are all very different.
It is imperative to know the exact type of stone that is to be maintained.
Stone is natural and may have adverse reactions to certain cleaning
chemicals and procedures. Most stones are also natural alkalis and so are
dirt and soil; therefore, stone and dirt are attracted to each other which
often makes cleaning very difficult. This makes the proper selection of
cleaning procedures and chemicals for stone very complex.
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Types of Stone:
The familiar stone types that are used today are identified through four
SEDIMENTARY, METAMORPHIC, IGNEOUS STONE, and 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.
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.
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
- 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.
- 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
CULTURED or FAUX MARBLE: A mix of resins that are painted or mixed with a
paint to look like marble.
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Currently, there are many companies around the world that use generic names
to identify different types of stone. This has created a problem for the
stone maintenance industry. The original names were in Italian. Usually the
name consists of two parts. The first part describes the color and the
second part describes the name from where the stone was quarried.
|ITALIAN NAME:||ENGLISH COLOR:|
Negro Marquina- Black Limestone from Marquina, Spain.
Bianco Carrara- White Marble from Carrara, Italy.
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There are many different types of stone available today. When stone is
ordered, it is fabricated with a particular type of surface. There are six
main types of surfaces that are selected:
Honed: Provides a flat to low sheen gloss. Different levels of gloss can be
selected. This surface is very smooth, but often very porous. This texture
is common in high traffic buildings. Honed floors should always be protected
with Stoneguard Penetrating Sealer because it has wide-open pores. Honed
stone colors are not as vibrant as a polished stone.
Polished: A glossy surface that wears away with time due to heavy foot
traffic and using improper maintenance procedures. This surface is very
smooth and not very porous. The reflectivity of polished crystals brings out
the brilliant colors and grains of natural stone. The shine comes from the
natural reflection of the stone's crystals. The polish is provided by
polishing bricks and polishing powders that are used during fabrication. The
shine is not from a coating.
Flamed: A rough surface that is developed through intense heat. During
fabrication, the stone is heated up and the crystals begin to pop, thus
forming a rough surface. This surface is very porous and must be treated
Tumbled: A slightly rough texture that is achieved by tumbling small pieces
of marble, limestone, and sometimes granite to achieve an archaic/worn
appearance. It often requires an application of Stone Color Enhancer to
bring out the colors.
Sand Blasted: This surface is the result of a pressurized flow of sand and
water that provides a textured surface with a matte gloss.
Sawn: A process performed by using a gang saw.
Bush Hammered: A pounding action that develops a textured surface. The
degree of roughness can be selected.
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As discussed previously, stone was formed from different types of natural
minerals. Marble's main consistency is calcium. Calcium carbonate is the
natural source that bonds the stone. Certain additive minerals blended in to
the calcium during formation to customize these brilliant colors. The
additive minerals are also color developers present in granite and other
|Black||Biotite, Hornblende, Carbon|
|Gray||Variety of minerals|
|Green||Mica, Chloride, Silicate|
|White||Feldspar, Calcite, Dolomite.|
|Augite||Brown, Green, Black, Purple|
|Biotite||Black, Brown, Green|
|Calcite||Pearlenscent and Pale Colors|
|Dolomite||Colorless, Pink, Pale Brown|
|Feldspar||Yellow, White, Pink, Green, Grey|
|Hematite||Metallic Grey or Black|
|Hornblende||Green, Yellow, Brown, Black|
|Limonite||Black, Brown, or Yellow|
Minerals have a variety of crystalline properties. A different property has
a different color. For instance, Augite (listed above) has different
crystalline properties. Each property has its own color. Stones brilliant
colors and various crystal formations developed when different mineral
properties blended together along with the integration of temperature and
The veins and color grains of marble were liquid minerals that flowed
through the stone when the Earth heated up. The intense heat softened the
limestone to allow the liquids to flow through it. When the Earth cooled,
the mineral flow stopped and gradually hardened to its current state.
The delicate colors of stone can often be altered by the improper use of
cleaning chemicals, mopping with dirty solution, using chemicals that are
not designed for stone care, and sunlight can fade the color of natural
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Reflectivity of Stone:
Stone contains natural crystals. These crystals reflect light to provide a
shine on the surface. When the crystals are dull, crushed, or broken, they
cannot reflect light evenly. For example, when the lens of a flashlight
breaks, it cannot reflect the light that is being emitted from the bulb.
Polished stone floors become dull when heavy foot traffic along with
sediment erodes the crystals. Normal footwear does not cause the main
damage, sediment and grit do. The sediment and grit that lies on the stone
surface is the main enemy of the stones crystals. The damage to the crystals
occur when the pressure from the shoe forces the sediment to abrade or
fracture the crystals.
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Hardness of Stone:
Marble is a relatively soft stone. On a measurement of hardness (MOHS),
marble is approximately a three out of ten. Marble is made of calcium, just
like your teeth. If you eat something to hard you will break your tooth. If
you eat a lot of sugar you will get a cavity. Stone reacts the same way. If
an improper chemical is applied to the surface, corrosion will begin to form
cavities in the stone.
Listed below is the famous Measurement of Hardness (MOH) Scale for stone.
This is a guide developed in the 1800's which helps evaluate the strengths
and weaknesses of the stone being used. For example, softer stones would
require the use of a less active chemical and a more frequent dust mopping
Measurement of Hardness Scale
- Calcite (Most Marbles)
- Feldspar (Granite)
- Quartz (Granite)
The objective of the MOH Scale is to measure stones resistance to hardness.
When sediment and grit are harder than the surface, they will scratch and
harm the stone. For example, a piece of hard plastic is about a 2.0. It will
not scratch #3 Calcite (Marble). However, a piece of sand that measures a 6,
will scratch #3 Calcite but will not scratch #7 Quartz which is Granite. The
harder the stone, the more resistant it is to abrasion. Exterior sediment
that is tracked in to buildings approximately measures from 3.0 to 7.0.
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*Article provided by Stone Care International Inc.