Indonesia Natural Stone Source
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What is Stone?
What is stone? The Oxford English Dictionary defines stone as "A piece of rock or hard mineral substance (other than metal), of small to moderate size". One of the most commonly used terms related to geology it derives from stan (Old English) and steinn (Old Norse). In the Gaelic it is clach.
The formation of sedimentary rocks was described in 1802, by Professor John Playfair, uncle to architect William, and friend of James Hutton, founder of modern geology. The notable 19th century Scottish geologist Sir Archibald Geikie eloquently commented on the process of transition from unconsolidated sediment to sedimentary rock: "If you take a quantity of mud, and place it under a weight which will squeeze the water out of it, you will find that it gets firmer. You can thus harden it by pressure. Again, if you place some sand under water which has been saturated with lime or iron, or with some other mineral that can be dissolved in water, you will notice that as the water slowly evaporates it deposits its dissolved material round the grains of sand and binds them together. Were you to continue this process long enough, adding more of the same kind of water as evaporation went on, you would convert the loose sand into a solid stone."
This is essentially the process of lithification (derived from the Greek word lithos – a rock). Thus in a sedimentary basin through compaction by the weight of overlying strata and by cementation by mineralised fluids so sedimentary rocks are formed. In contrast, igneous rocks are usually consolidated by crystallization of minerals from molten material either within the earth’s crust (e.g. granites) or at the surface (e.g. basalt lavas). As their name suggests metamorphic rocks have been transformed (recrystallised) from the original rock by a combination of heat and pressure. In these circumstances, new minerals sometimes form.
Choosing the Right Stone
As building material, stone has several positive features:
• It is easily available
• When correctly processed, stone is a stable, almost eternal material.
• It is non-flammable.
• Its appearance is natural and unique.
To enhance these features, the aesthetical and mechanical properties that determine the possible uses of a rock type must be understood in the planning phase. Only then can a long-lasting, beautiful result be achieved. There are couple of things to look at:
Outer Appearance
The outer appearance of rock types varies. Stone is a natural product. The texture and colouring of the material vary, contributing to its unique appearance. Surface treatments can either enhance or fade the surface colours and patterns.
Mechanical Properties
During dimensioning and attachment methods management, the mechanical properties of stone slabs must be taken into consideration. The weather resistance and susceptibility to discolouring are also estimated. The European Committee for Standardisation, CEN, has defined standard methods for the testing of mechanical properties. These are some descriptions for types of Mechanical Properties:
Water absorption
Water absorption is measured as mass percentage of dry weight. The water absorption of porous rocks is greater than that of dense rock types. As a result, porous rocks are susceptible to discolouring and have poor frost resistance. The values for dense rock types vary between 0.1 and 0.5 mass percents. The absorption value for porous rock types may exceed 20. A rock will have good frost resistance, when its water absorption is less than 0.5 mass percents.
Hardness
Measured by scratching the surface with mineral. Values are reported in Mohs' hardness, a scale of 1 to 10 Mohs, where the hardest rock will receive the value 10. This value can be used in estimating durability and persistence.
Thermal transformations
Thermal transformations are changes in volume that are caused by temperature changes. These properties are necessary in evaluating the need for expansion joints in structures. The thermal transformations of natural stone vary between 0.2 - 0.9 * 10^-5/C, and are less than with most building materials.
Humidity transformations
Humidity transformations are changes in volume that are caused by changes in humidity. Only the thin marble tiles have been shown to respond notably to changes in humidity. Marble tiles tend to bend unevenly when they get wet. For other rock types, this property bears little significance.
Abrasion resistance
Abrasion resistance must be considered when selecting the surface treatment, if the abrasion burden is significant. The European Union has issued a standard for abrasion resistance.
Breaking around a fixing point
The likelihood of stone breaking around a fixing point depends on several factors: the size of the stone slab, the quality and quantity of fixing points, and the hardness of the rock type. The sufficient value of 2 - 5 kN can usually be attained, when the slab is 30 mm thick.
Weather resistance
In the long run, weather resistance plays an important role in the durability and appearance of facades. Exposure to the climate and weather conditions may result in discolouring or colour changes, diminished polish, chemical and mechanical weathering, and in bent stone slabs. Different rocks have different weather resistance properties.
Igneous rocks (e.g. granite)
In igneous rocks, exposure to climate and weather conditions causes mainly surface discolouring. Surfaces with bush hammer finish are easily discoloured, but on a polished surface discolouring is close to non-existent.
Limestones and Marbles
Alkaline rock loses its shine and strength in acidic urban atmosphere. In only ten years, exposure to acid rains will result in severe weathering and cause limestone and marble to become brittle.
Choosing the Stone
Stone Type/Property
Granite - Marble - Calcite - Limestone density "a" - Limestone density "b" - Sandstone - Schists
Density min kN/m
25,6 - 25,9 - 17,6 - 25,6 - 22,4 - n/a
Water absorption max (mass percent)
0,4 - 0,75- 12 ,0 - 3,0 - 20,0 - 0,25
Compressive strength/Compression resistance min (MPa)
130,0 - 52,0 - 12,4 - 55,2 - 13,8 - n/a
Abrasion resistance min
10,0 - 10,0 - 10,0 - 8,0 - 8,0
Availability
It is advisable to determine the availability of a rock type before making the final selection. While planning, it is wise to have a few alternatives before confirming the order of the material. The project schedule should also be planned only after receiving confirmation on the availability of the chosen rock. Depending on the degree of processing, it may take 2 to 6 months before the ordered slabs are ready to be assembled.
Slate Information
Slate is formed through metamorphism, a process in which the tiny elements that make up a rock are pushed closer together to form a crystalline structure, also known as recrystallization of the stone. This all occurs while the stone is in a solid state, and the materials that make up the stone are not changed, they are merely repositioned to be closer to one another in a crystal pattern. Metamorphism can be caused by heat or pressure. The materials which undergo this transformation to form slate are generally a shale type sedimentary rock.
Slate forms in layers that easily cleave off in thin lines, generally known as Slaty Cleavage. During formation the original sedimentary rocks are forced down into these plains due to immense pressure. The resulting slate can be comprised of many different beds of sedimentary rock, all of which are now reoriented in the same direction.
While slate is generally a grey or grey-blue color, it can also have multicolored effects in its surface. These come from the various different beds of sedimentary rock from which it is derived, often making this material a contrast of hues.
Slate is most commonly used for roofing because it can be sliced into thin layers. It is also very popular in flooring, countertops, and architectural applications, due to its durability, its natural beauty, and it’s relatively low cost. Its clefted surface makes it slip resistant, causing it to be popular in kitchens, bathrooms, and restaurants, as well as public hallways and other high traffic areas. It is also used in decorative home furnishing, fish tanks, and even in novel accessories such as board games.
Slate is found naturally in mountains. When it is quarried, it is usually done so in large blocks known as slabs. These blocks are then chopped up into smaller slabs for distribution. The size of the slab they can make is dependent on the relative strength of the type of slate. The inherent layering of this material makes some rather large sizes difficult to maintain and keep from cracking.
In stores, slate is generally available in tiles of various sizes including 16X16, 12X12, 8X8 as well as in slabs of various sizes, usually running to about 80 inches in length. Installations are generally done with mortar backing to even out varying thicknesses. Then grout lines are run along the joints of the stones. It is important to adequately seal and protect all tiles before grouting them.
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 natural stones.
Stone Color - Mineral
Black Biotite, Hornblende, Carbon
Brown Limonite
Gray Variety of minerals
Green Mica, Chloride, Silicate
Red Hematite
White Feldspar, Calcite, Dolomite.
Yellow Limonite
Mineral - Mineral Color
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
Sulphur Pale Gold
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 pressure.
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 minerals.
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Stone Surface & Textures
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 with Stoneguard.
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.
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 program.
- Talc
- Gypsum
- Calcite (Most Marbles)
- Fluorite
- Apatite
- Feldspar (Granite)
- Quartz (Granite)
- Topaz
- Corundum
- Diamond
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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Types of Stone
The familiar stone types that are used today are identified through 4 categories:
- SEDIMENTARY
- METAMORPHIC
- IGNEOUS STONE
- MAN-MADE.
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
History of Natural Stone
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.
