Sedimentary
Stone
Sedimentary
stone is formed when organic matter accumulates
and consolidates in layered deposits at the
bottom of lakes and in the sea. Over millions
of years the layering causes the weight of the
rock beds to increase. Eventually the pressure
produces a chemical reaction that causes the
sediment to harden and turn into stone. Examples
of sedimentary stone commonly used in building
include limestone, travertine and sandstone.
Most sedimentary stones are rated around a 3
on the Mohs Scale of hardness.
Limestone
Limestone is a soft stone,
primarily formed from calcium rich organisms
like seashells and bones. It is commonly used
as a building material as it is easy to manipulate
and readily available. It has a smooth surface
and can vary in hardness. It contains the mineral
calcite however some limestone also contains
magnesium, which makes it harder and allows
it to take a polish like marble. This harder
limestone is also more weather resistant. A
type of limestone known as fossil stone contains
visible fossils including seashells and plants
however this is quite porous and cannot be polished.
Limestone is used to produce benchtops, fireplaces,
floors, vanities, ornamental pieces, interior
and exterior wall cladding and paving. It is
prone to absorbing oil, water and other liquids
therefore it must be protected with a penetrating
sealer. It can also scratch and is sensitive
to acidic substances such as juice and wine.
The softer varieties of limestone are not recommended
for high stress areas.
Colours are usually soft and include grey,
light beige to tan, white, pastel pink, green
and yellow.
Travertine
Travertine
is a soft, porous type of stone made from the
calcium in limestone and usually found near
natural springs. The calcium is washed from
the limestone bed by hot spring water. It floats
to the surface where the water evaporates leaving
a layer of crystals. As this process continues
over time, many layers are produced. Carbon
dioxide bubbles become trapped in the layers
as the stone is being formed. Holes caused by
these bubbles are typical in travertine.
Travertine is not particularly hard wearing,
but if the holes are filled with cement or resin
during the manufacturing process, it can be
honed or polished and used in high traffic areas.
It is mainly used to produce interior and exterior
wall cladding, exterior tiles, paving and curbing,
furniture and vanities etc. Like other limestone,
travertine is sensitive to acidic substances
such as juice and wine and must be sealed with
a penetrating sealer.
Colours are usually cream, beige, brown, pink,
red and gold.
Sandstone
Sandstone is a soft stone, formed when sand
containing a variety of minerals including quartz,
pyrite, iron, silica, calcite and some organic
matter are cemented together by pressure. Other
minerals, which give sandstone its character
and add colour include mica, hematite, feldspar,
ilmenite and clay minerals.
Sandstone was commonly used in the construction
of buildings and bridges up to the 1800’s,
prior to the introduction of reinforced concrete.
It is a strong and durable stone with a matt
finish and has excellent slip resistance. It
can have a fine or coarse texture and is particularly
suited to outdoor pool areas. Sandstone is used
mainly to produce interior and exterior flooring,
paving and walls. It is porous and must be sealed
with a penetrating sealer.
Colours are usually cream, brown, red, grey
and sometimes green, depending on the minerals
covering and cementing the sand, for example
sandstone that contains iron will be red to
brown, whereas sandstone with a silica content
will be more white.
Metamorphic
Stone
Metamorphic stone is formed when existing igneous
and sedimentary rock is buried deep below the
earth’s surface and exposed to extreme
heat and pressure over millions of years. It
is called metamorphic because “meta”
means change and “morph” means form
and that is what it does – the rock changes
its composition, texture and colour. Examples
of metamorphic stone commonly used in building
include marble, serpentine, slate and onyx.
Most metamorphic stones are rated around a 3-4
on the Mohs Scale of hardness.
Marble
Marble is a soft stone that is formed in the
earth’s crust through the metamorphic
process. It is classed as a non-foliated metamorphic
rock as it is not layered like slate. It is
formed mainly from limestone reacting to the
extreme heat underground but not directional
pressure. It mainly contains the minerals calcite
and dolomite, however impurities in the original
limestone recrystallise to form other minerals
that create a variety of colours in the marble.
White marble contains more calcite, yellow marble
contains limonite, reddish marble contains hematite
and green marble contains serpentine. It also
has a wide variety of vein like patterns, which
add to its appeal. These veins are created when
minerals in the stone liquefy due to the heat
in the earth’s crust, then flow through
the stone and solidify as the earth cools.
Marble is a popular stone commonly used for
its strength and beauty and its ability to achieve
a ‘mirror like’ finish when polished.
It has been used for centuries as a building
material and also to create sculptures, as it
is soft but strong. It is a versatile material
also used for floors, furniture, vanities, bathroom
tiles and ornaments. Although it is fairly resistant
to erosion and fire, acidic liquids will etch
the surface and grit will scratch it. It is
not an ideal surface to use as a kitchen benchtop
where spills and scratching are common. Its
longevity will be determined by its treatment
and maintenance. Sealing with a penetrating
sealer is recommended, and will protect the
surface from staining. Regular cleaning with
recommended products will prolong the glossy
look and feel of the marble.
Colours are usually white, red, black, green,
yellow and various shades of these colours.
Serpentine
Serpentine (Green Marble) is a soft, silky
feeling stone, formed in the earth’s crust
during low-grade metamorphic conditions. It
is classed as a non-foliated metamorphic rock
as it is not layered like slate. The pattern
in the marble is said to resemble a serpent’s
skin, hence its name. Its green colour is mainly
due to the magnesium content.
Serpentine is often used for furniture and
ornaments, as it is soft and ideal for carving.
It is also used in jewellery and is sometimes
mistaken for jade. It is not a stone that weathers
well and is therefore suited to indoor applications.
Unlike other marble and limestone, serpentine
is not affected by acidic liquids and therefore
can be used for kitchen benchtops. Thin slabs
of serpentine may be used for wall panelling,
and stair treads. Although it will take a polish
it does not have a highly reflective finish.
Colours are usually yellowy green, olive, dark
green, brown, grey and black. It usually has
a white vein, a soft, waxy feel and an opaque
to translucent look.
Onyx
Onyx is a soft, fine-grained stone made from
calcium layered under extreme heat and pressure.
The layering occurs in limestone caves when
water drips over limestone and redeposits forming
stalactites and stalagmites. The name onyx has
Greek origins and means claw or fingernail which
has a similar translucent appearance to onyx
stone. It is mainly found in the USA, Germany,
Brazil, Mexico, India, and Africa.
Onyx is known for its opalescence or translucence,
spectacular patterns and vibrant colours. It
is not a stone that should be subject to hard
wear as it is quite soft. It must be professionally
sealed with a penetrating sealer otherwise stains
can be difficult to remove. Onyx etches with
acidic liquids and must be maintained with care.
It can be used to make tiles, tables, hand basins,
vases, bowls and ornaments that can be backlit,
as the light will shine through the stone. Onyx
products are usually highly polished to bring
out the beautiful patterns and colours in the
stone.
Colours range from earthy reds, browns and
greys to a variety of pastel greens, creams,
gold, amber and white.
Slate
Slate is a fine-grained, foliated stone formed
under the ocean when layers of sedimentary rock,
clay, shale or quartz are compressed under low-grade
heat and pressure. Due to its layering, slate
can be easily split, exposing a range of magnificent
textures. It is mainly quarried in Africa, China,
Brazil, Italy, USA, UK and India and can range
from very soft to hard depending on its origin.
Soft slate is found in the USA and hard slate
in the UK.
Slate is popular for both indoor and outdoor
use because of its beauty, strength and rustic
appearance. It was traditionally used on roofs
as shingles, in blackboards and for headstones.
It is now commonly used around pools, for landscaping,
floors, roofs and wall cladding, in large and
small scale construction.
Once installed slate is a particularly durable
surface, resistant to wear, especially in areas
where there is a large amount of foot traffic.
It is heat, fire and weather resistant, non-porous,
so spills are not absorbed and highly resistant
to acidic liquids. It is slip resistant due
to its surface texture and retains warmth. There
are some softer slates however that can break,
chip and scratch so the environment must be
considered when choosing a slate. A good quality
penetrating sealer will provide added protection
and strength. Slate can also be coated with
a wet look sealer to protect it and enhance
its appearance.
Colours are usually shades of black, grey,
green, brown, yellow, purple, pink and sometimes
copper.
Igneous
Stone
Igneous stones are exposed to extreme heat,
hence the name ‘igneous’, which
comes from the Latin word ‘ignius’
meaning fire. Igneous stone is either ‘intrusive’
or ‘extrusive’. ‘Intrusive’
stone is formed underground where rock located
up to 40km under the earth’s surface melts
at temperatures of up to 900?c and becomes magma.
The magma rises and cools slowly, trapping gases
and minerals, and eventually solidifying into
stone that has large crystals and a coarse texture.
Granite is ‘intrusive’ stone. ‘Extrusive’
stone develops above the earth’s surface.
It is formed from lava that flows from volcanos
on to the earth’s surface and into the
sea, or from volcanos under the sea. The lava
settles on the earth or on the ocean floor and
cools. The faster cooling process, due to the
lower temperature at the earth’s surface
and under the ocean, encourages smaller crystals
to form. Basalt is ‘extrusive’ stone.
The most popular igneous stones used in building
are granite and basalt. Both contain large quantities
of quartz and silica, but it is the heavy metals
such as iron and magnesium that give the stones
their dark colour.
Granite
Granite
is a hard ‘intrusive’ stone, extremely
durable, strong and coarse grained with large
crystals, which give it a flecked look. It mainly
contains the minerals potassium, feldspar and
quartz with small amounts of mica. Most of the
continent is made of granite.
Granite is one of the hardest, most popular
building materials used in the world and is
commonly used indoors for kitchen benchtops,
bathroom vanities, floors and furniture. Outdoors
it is used in large structures such as bridges,
monuments, retaining walls and steps and in
large public floor areas due to its solid character
and ability to withstand deterioration. Granite
is usually used as a slab rather than a tile,
so its weight must be considered when choosing
an application.
Polished granite is hard wearing, easily maintained,
heat, chip, bacteria, fire and scratch resistant
and is not affected by acidic liquids such as
juice, coffee, tea and wine when treated with
a good quality penetrating sealer. Granite has
an ageless beauty, is longer wearing than manmade
stones and will retain its colour and finish
longer than other stones.
Colours are usually shades of black, grey,
brown, red, pink and yellow, which are determined
by the minerals trapped when the stone is forming.
Basalt
Basalt
also known as bluestone is ‘extrusive’,
hard stone, fine-grained with small crystals.
Most of the ocean floor is made of basalt. Basalt
was traditionally used for cobbled roads and
laneways due to its durability and because water
drained away from the surface efficiently allowing
it to dry quickly. It was also popular due to
its texture, which made it a non-slip surface.
It is now commonly used in outdoor areas for
paving, stairs, exterior wall cladding, ponds,
landscaping, pathways and indoors for countertops,
walls and floors.
Colours are usually blue/grey, green/grey,
grey and black.
Manufactured
Stone
Manufactured
stone also known as manmade or engineered stone
is usually made from a mixture of resins, cement
and natural stone chips such as marble, granite,
and basalt or quartz and coloured pigments.
The materials are mixed together, highly compacted
into a dense form, cured in a kiln, cooled,
cut into sheets and polished. Most manufactured
stones are designed to imitate the popular textures
and colours of natural stones, especially granite.
Benefits
