Stones

GENERAL OF STONE

• In geology, stone is a naturally occurring solid aggregate of minerals or mineraloids.
• Stone are also known to geologists as rocks.
• The Earth's outer solid layer, the lithosphere, is made of rock.

   Stones can be either;

    - artificial

    - natural

ARTIFICIAL STONES

Artificial stone or engineered stone is a name for various kinds of synthetic stone products used from the 18th century onward. They have been used in building construction, civil engineering work, and industrial uses such as grindstones.


One of the earliest was Lithodipyra (aka Coade stone), a ceramic created by Eleanor Coade (1733–1821), and produced from 1769 to 1833. Later, in 1844, Frederick Ransome created a Patent Siliceous Stone, which comprised sand and powdered flint in an alkaline solution. By heating it in an enclosed high temperature steam boiler the siliceous particles were bound together and could be moulded or worked into filtering slabs, vases, tombstones, decorative architectural work, emery wheels and grindstones.


This was followed by Victoria stone, which comprises finely-crushed Mountsorrel (Leicestershire) granite and Portland cement, carefully mixed by machinery in the proportions of three to one and cast in moulds of the required shape. When the blocks are set hard the moulds are loosened and the blocks placed in a solution of silicate of soda for about two weeks for the purpose of indurating and hardening them. Many manufacturers turn out a material that is practically non-porous and is able effectually to resist the corroding influence of sea air or the impure atmosphere of large towns.


Most later types of artificial stone have consisted of fine cement concrete placed to set in wooden or iron moulds. It could be made more cheaply and more uniform than natural stone, and was widely used. In engineering projects, it had the advantage that transporting the bulk materials and casting them near the place of use was cheaper than transporting very large pieces of stone.


Modern Cast stone is an architectural concrete building unit manufactured to simulate natural cut stone, used in unit masonry applications. Cast stone is a masonry product, used as an architectural feature, trim, ornament or facing for buildings or other structures. Cast stone can be made from white and/or grey cements, manufactured or natural sands, carefully selected crushed stone or well graded natural gravels and mineral coloring pigments to achieve the desired colour and appearance while maintaining durable physical properties which exceed most natural cut building stones. Cast stone is an excellent replacement for natural cut limestone, brownstone, sandstone, bluestone, granite,  slate, coral rock, travertine and other natural building stones.

The natural stones used in the manufacture of  artificial stones can be either:

1. Calcareous stone materials; such as marble, limestone or dolomite.

2. Siliceous stone materials; such as granite, quartzite, sand, porphyry, etc.

Aesthetic appearances of artificial stones vary according to the nature, colour and quality of the aggregate used as well as the bonding (cement) paste. It is possible to manufacture products having special made-to-measure aesthetic visuals to meet the demands of architects and building owners.

Versatility is one of the major features of artificial stones. The wide dimensional range and aesthetic appearance make them ideal for;

·         outdoor and indoor floorings,

·        outside claddings,

·         internal facings,

·         steps,

·         raised floor systems,

·         window sills

Artificial stone

Outdoor and indoor flooring with artificial stone

Outside cladding wall

Artificial stone step

Raised floor system

Artificial marble stone window sill

Manufacturing Process

A mixture of the raw materials; crushed stones and the bonding agent (cement or sometimes polymers), is compacted by vibration under vacuum to produce:

1.  Slabs (tiles),

      Where thin monolayer tiles of the required sizes are produced.

2.  Large-size blocks.

      These blocks are then sawn into slabs to be transformed into finished products with the required sizes.

NATURAL STONE

Stones are made up of a mosaic of interlocking mineral grains that have definite chemical compositions. Minerals have been divided into groups. The groups we are primarily concerned with are the Common Rock Forming Mineral Group which can be subdivided into two mineral categories Silicates and the Carbonates. Silica is the most common chemical component of the earth. Silicates which contain silica are generally the harden minerals and the most common rock-forming minerals.These stones can be referred to as Siliceous based stones. Carbonates are the next most important minerals in the rock-forming group. This mineral group generally contains the softer minerals. These stones can be referred to as Calcareous based stones. Stone used in building are obtained by taking rocks from the earth and cutting them to the sizes and shape for construction. Rocks or Stone can be divided into three major groups there are igneous rocks, sedimentary rocks, metamorphic rocks.


PHYSICAL PROPERTIES OF NATURAL STONE

Permeability
Associated with stones porosity is its permeability. This is the extent to which the pores and capillary structures are interconnected throughout the stone. These networks, their size, structure and orientation affect the degree and depth to which moisture, vapors and liquids can be absorb into the interior of the stone or migrate from the substrate by capillary action through the stone. Permeability may be greater in some directions than others based upon the pore size, shape and the distribution of the interconnectedness of the system. Permeability is increased when a stone is highly fractured or the veining material is soft or grainy. A particular variety of stone may be highly permeable ( a well defined interconnected network of pores), although its porosity is low (a low percentage of voids). The size and shapes of pores and the capillary structure differs in stones and is an important factor in relation to stone decay.

Absorption
Absorbency is the result of these two properties. Absorbency is an important determining factor in stone sensitivity to stains. The size of the pores, their orientation, how well they are networked and the type of finish the stone has are important contributing factors to a stones overall absorbency. In relation to cleanability this factor is more important than how porous a stone is. Honed and textured surfaces are more susceptible to soiling and staining due to the fact that there are more open pores at the surface than a highly polished finish. The polishing process has a tendency to close off pores leaving fewer ones exposed, resulting in a low absorbent surface. However, some varieties of stone have large pores and capillary structures and even when these stones are polished they still remain very absorbent.

Durability
Natural stones are generally extremely durable but deterioration may result from wrong choice of stone being exposed to the weather elements. Other causes of deterioration include faulty design and workmanship, atmospheric pollution, soluble salt action, frost, wetting and drying, solution, rusting of ferrous metals and vegetation growth. Another that, The environmental conditions vary with exterior or interior, vertical and horizontal applications. Climatic conditions ranging from a freeze/thaw climate, a dry hot desert environment and coastal exposure. Wet conditions such as around pools/spas and in bathrooms (showers). High traffic pedestrian areas, etc. Another factor of stones durability is its Aesthetic Durability or Dimensional Stability. Cosmetic changes may occur. This has to do with the Color Stability of certain stones. These changes can take place in two ways.
SUNLIGHT :
When some stones are used in exterior applications and exposed to direct sunlight they fade or change color. Dark colored stones and those that contain organic matter will generally fade to a much lighter color. A personal experience I encountered involving color stability involved an interior/exterior installation of a crimson colored Coralstone. The exterior corel stone in the direct sunlight had faded 2 to 3 shades lighter in color. The interior stone had not experienced any color change. The corelstone being of a biogenic origin contained organic material that was affected by ultraviolet exposure.
MOISTURE :
Some stones have moisture sensitive mineral contents that will cause the stone to develop rust spots, or other color variations, or contain moisture sensitive substances that will cause blotchy and streaking discolorations. Certain limestone's contain bituminous materials that are soluble when exposed to moisture. Some marbles are also moisture sensitive when in high moisture areas, showers and those with steam features, these stones have a tendency to develop dark botches.
It needs to be emphasized...that because a particular stone will not perform well when subjected to certain environmental conditions, that this means the stone is of poorquality. Almost all of the problems that occur with stone are because the particular type of stone was not selected correctly for the use for which it was intended.

Salt Decay
Soluble salts present in the stones, exert expansive force when they crystallize and are the chief cause of progressive decay.In another word ,salts are some of the most damaging agents to stone. Salt manifest themselves in a process commonly referred to as efflorescence. There are several different types. The most common form of efflorescence is the appearance of salts at the surface in the form of whitish to gray powdery fluffy blooms. This occurs when the stone, substrate or other sources of soluble salts are in contact with moisture and move to the surface by capillary action. As the moisture moves to the surface these soluble salts are deposited at the surface to recrystallize into these blooms. This form is generally harmless. Subflorescence is similar to efflorescence, however instead of the salts being transported to the surface they crystallize and buildup within the pore/capillary structure beneath the surface. As the salts accumulate internal pressures develop generating spalling and flaking and may eventually lead to deep deterioration of the stone. Numerous varieties of salts have been identified in the efflorescence process. Some of these varieties by themselves or when combined with others will form a "hard and glassy skin" adhering rather strongly to the surface. This type is Crystalline efflorescence.

Frost Action
Frost action or commonly called freeze/thaw cycles occur when water within the pore structure or cracks freezes to ice. It has been estimated when water freezes it expands between 8 to 11 percent, with a force of 2,000 pounds per square inch to 150 tons per square foot. This increase of internal pressure combined with repeated freeze/thaw cycles produces micro-fissures, cracks, flaking and spalling.

Wetting and Drying
Coefficients of expansion and contraction are also involved in volume change. Stone expands when it absorbs water and shrinks as it dries. This expanding and contracting produces internal stresses at the grain boundaries. When the stone heats up a "baking effect" occurs, which will eventually lead to surface flaking. Marble is affected by this "baking effect."

Thermal Expansion
Different minerals expand and contract at different rates, this is known as the coefficient of heat expansion and contraction. It is known that the temperature of stone can vary between 30 and 50 percent higher than the average air temperature. Some of the darker minerals, absorb heat more readily, and also give it up more quickly than some of the lighter ones. The daily and seasonal heating and cooling of stone can cause stresses and micro-fractures in and along mineral grains.Water in the pores makes thermal stressing more effective. This can eventually produce surface flaking. Marble is particularly affected by this.

CHEMICAL PROCESSES

Involves complex chemical reactions that alter the internal structure of minerals by removing and or adding elements through...dissolution...oxidation...hydration...hydrolysis.
Water, in all of its occurrences (rain, fog, raising ground moisture, ocean, etc.) and its chemical composition is the most important element in this process. It acts as a solvent and also as a chemical reactant. Carbon dioxide (CO2) and oxygen are also important agents along with climatic conditions.

Dissolution :
This is a process whereby some minerals or part of the chemical composition of a     mineral can be dissolved in water. When an acidic element is added to the water it increases its ability to dissolve minerals more readily, particularly those containing calcium, magnesium, sodium and potassium. The atmosphere is a mixture of gases and one of these natural occurring gases is carbon dioxide, CO2. CO2 is also produced by the combustion of fuel and released into the atmosphere. When CO2 gas is dissolved in water it is converted to carbonic acid, and a carbonated solution is formed. Just a small amount of acid increases the corrosive effects of water. Limestone and marble are particularly subject to this process. In exterior installations, they can develop a petted surface and if they have a polished finish they will lose it. Sandstone that contains calcite is also affected. The calcite can be leached from the stone and may result in a flaking or spalling of the surface and in some incidences may cause the stone to crumble.Rain is naturally acidic. This is the primary reason why polished marble and limestone in a exterior installation will not hold a polished finish.

Oxidation :
Oxidation, also referred to as "rusting" occurs when oxygen assisted by moisture combines with iron-bearing minerals. Oxidation is accelerated by moisture and high temperatures. It is an important process in the alteration of iron and magnesium rich minerals. Mineralogically iron occurs in three states...metallic...ferrous (Iron II)...ferric (Iron III). During the oxidation process Iron II is converted to Iron III resulting in color changes and a weakening of the mineral structure. Ferrousmagnesian silicate minerals that undergo oxidation are responsible for the appearance of rust spots on some granite-type stones. When marble or limestone contains sulfide minerals such as pyrite, and it undergoes oxidation, the Iron II in this composition will produce rust spots and the sulfur is converted to sulfuric acid which can dissolve the calcium producing pitting. Iron oxide minerals are common in sandstone and over time may develop rust spots.During the oxidation process an increase in volume of the mineral structure can occur, usually making it softer and weaker and rendering it more vulnerable to other elements of the chemical weathering processes.

Hydration :
Hydration is the chemical addition of water molecules to a mineral. This process frequently produce a new mineral compound. In addition, the size of the mineral structure is increased causing stress and developing zones of weakness. This can increase the overall permeability of the stone and lead to spalling, pitting and flaking. Overall color changes can take place as well.

Hydrolysis :
This is the dissolution and alteration process that affects silicate minerals in granite-type stones. As with the dissolution process the addition of a acidic ingredient is an important element in this process. Feldspars are an important silicate mineral group in granite and granite-type stones, with their general formulas containing potassium, sodium and calcium. These soluble elements are leached out during the chemical reaction with acidicly charged waters and carried away. As the process proceeds permeability increases exposing more mineral surface to the process, the mineral grains will eventually weaken leading to spalling and crumbling. Once this process has started it is irreversible.

RATES OF WEATHERING

Intensity and duration are two key elements that govern to what extent weathering reactions will have on stone. When the presence of pollutants like nitrogen and sulfur-bearing gases are in the atmosphere and combined with water (rain and fog) they form powerful acids. Acid rain and fog have accelerated the weathering processes to several times that in unpolluted areas. The pH of rain is naturally acidic, with a pH of approximately 5.6. This is the result of the natural occurrence of carbon dioxide in the atmosphere being dissolved in atmospheric moisture to form carbonic acid. Combine this natural occurring process with the addition of sulfur dioxide and nitrogen oxides which are transformed into sulfuric and nitric acids when combined with water, and its corrosive forces have been dramatically intensified. The average pH of acid rain is about 4.4, ten times stronger than normal rain. It also has been estimated that about half of these two pollutants are not mixed with atmospheric moisture and settle back to the earth as aerosols, (dry gases and dry particles). These acidic aerosols when combined with the next rain produce an even stronger corrosive solution. The concentration (intensity) of acidic solutions have a direct effect on the rate at which the weathering processes occurs. In addition to the intensity factor, is the duration or length of time and frequency that a process is active. Prolonged and frequent exposure accelerates the rates of weathering. Several other factors influence the type and rates of weathering, alterations and decay of stone. The most important of these are...composition of the stone...physical condition of the stone & environmental conditions.

Composition of the Stone :
Its mineral and chemical composition are important factors as to the extent to which the stone will be affected and the type of effects it may display. Generally...
Granite-type stones :
are more resistant to the mechanical processes with the exception of salt decay and more susceptible to the chemical processes of hydrolysis and in some cases oxidation.
Limestone and marble :
are vulnerable to salt decay, dissolution, hydration and in some cases oxidation Sandstone is susceptible to the processes of salt decay, oxidation and if it is a calcareous variety of sandstone, it is vulnerable to the dissolution process.
Clay slates :
are vulnerable to the chemical processes of hydration, hydrolysis and some varieties are affected by the oxidation process.

Physical Conditions :
This involves its physical features, such as its pore/capillary structure, visible and micro-fractures, bedding planes and the finish of the stone, natural cleft, textured, honed and polished. These physical features relate to water/moisture pathways into the interior of the stone and mineral surfaces that will be exposed to the chemical and mechanical processes.

Environmental Conditions :
The environment that the stone is in can be said to be the most significant factor upon the type and rates of weathering alteration and decay. The chemical processes are more pervasive and rapid in a warm and moist environment. Salt decay is also a prevalent process in this kind of environment as well.

Some other contributing factors to the rates of weathering, alteration and decay may be the results of improper maintenance procedures, faulty restorations, improper preservation treatments or methods, etc. Any of these may accelerate the processes. There is another aspect to the natural weathering / alteration process which is often misunderstood. This involves understanding that some stones due to their natural characteristics will naturally experience some sort of appearance change. One example of this is...Some limestone's will develop a patina which actually gives the stone more character and offers a certain amount of protection as well. However, the prevailing mindset that has been developed by the consistent uniform appearance of man made and synthetic building materials fosters the idea that something wrong is happening with its appearance. It should be understood that what is taking place in this particular situation is a natural occurring process. It needs to be emphasized, that all stone will experience the natural weathering process to a certain degree. However, understanding the natural characteristics of the stone and the weathering processes that affect them, proper maintenance and preservation programs can be employed to minimize and manage their effects.


MAIN TYPE OF NATURAL STONE

Natural stone divide into three main type :

·         Igneous rock: Granite, basalt, pumice

Igneous comes from the root word "ignis," which means, "of fire". Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust  for example granite, while volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta for examples pumice and basalt

Below is a summary of the major characteristics of igneous rocks.

      Classified by texture and composition

      Normally contains no fossils

      Rarely reacts with acid

      Usually has no layering

      Usually made of two or more minerals

      May be light or dark colored

      Usually made of mineral crystals of different sizes

      Sometimes has openings or glass fibers

      May be fine-grained or glassy (extrusive)

Some Common Igneous Rocks
Name		Color	Texture
Granite		Pink/Gray	Intrusive
Gabbro		Dark Gray to Black	Intrusive
Rhyolite		Light Pink or Gray	Extrusive
Basalt		Dark Gray to Black	Extrusive
Obsidian		Usually Dark Colored	Extrusive
Scoria		Dark Colored	Extrusive

Granite

Gabbro

Rhyolite

Basalt

Obsidian

scoria

·         Sedimentary rock: limestone, sandstone, dolomite

There are four main types of sedimentary rocks :

v  First there are the types that are the result of some preexisting rock'sdemise through the weathering process (rocks broken down by the action of water, wind or ice). Sandstone "Siliceous"

v  The second kind is biogenic, stone produced by living organisms(organic material such as marine creatures or vegetation which eventually died and the remains became part of the sediment on the bottom of ancient sea beds. Certain Limestone's, Coralstones, Fossilstone, Shellstone "Calcareous"

v  The third is produced by inorganic chemical material being deposited on the floor of ancient sea, lake beds and springs through the process of precipitation or evaporation. The white fur deposits in kettles in which hard water has been boiled is a good example of this type of stone. Certain Limestone's and all Travertine's. "Calcareous"

v  The last sedimentary category are produced as a result of volcanic activity. This stone is composed of volcanic ash with a variety of secondary older rock materials from the surrounding area, volcanic and igneous in nature. This category is considered a tuff sedimentary stone. It is also classified as a igneous stone due to its volcanic origin.
Cantera and Adoquin are of this variety. "Siliceous"

Sediments can harden into sedimentary rock in two ways.

      pressure-As layer after layer of sediments are deposited, the lower layers are pressed together tightly under the weight of the layers above.

      cementing-Some sediments are glued together by minerals dissolved in water.

Below is a summary of the major characteristics of sedimentary rocks.

      Classified by texture and composition

      Often contains fossils

      May react with acid

      Often has layers, flat or curved

      Usually composed of pieces cemented or pressed together

      Has great color variety

      Particle size may be the same or vary

      Usually has pores between pieces

      May have cross-bedding, mud cracks, worm burrows, raindrop impressions

Some Common Sedimentary Rocks
Name		Color	Composition
Sandstone		Red or Gray	Sand grains cemented together
Limestone		White to Gray	Calcite and sometimes fossils
Shale		Dark Gray	Compacted mud
Conglomerate		Different Colors	Rounded cobbles and pebbles cemented together

Sandstone

Limestone

Shale

Conglomerate

·         Metamorphic rock :

Metamorphic is derived from the Greek meta denoting a change and morph meaning form ‘a change in form’. This changing of one rock type into another new type takes place by an increase in temperature or pressure or a combination of both. The original minerals of the stone recrystallize, small crystals merge to form larger crystals with no changes in the mineral chemistry, fine-grained calcite in limestone recrystallizes to a coarse-grained calcite crystal structure in marble; or there may by a transformation into a different set of metamorphic minerals. This recrystallization transforms the Shale into a colorful Slate "Siliceous". Limestone becomes a multi colored Marble "Calcareous" and the grainy Sandstone alters into a highly crystallized sparkling Quartzite "Siliceous". Metamorphic rock just like caterpillar transforms into a beautiful butterfly.

Below is a summary of the major characteristics of metamorphic rocks.

      Classified by texture and composition

      Rarely has fossils

      May react with acid

      May have alternate bands of light and dark minerals 

      May be composed of only one mineral, ex. marble & quartzite

           May have layers of visible crystals

           Usually made of mineral crystals of different sizes

           Rarely has pores or openings

           May have bent or curved foliation

Some examples of how metamorphic rocks were changed:

Original material	Metamorphic stone
Clay	Slate
Limestone	Marble
Sandstone	Quartzite

 

Some Common Metamorphic Rocks
Name		Color	Texture
Gneiss		Pink/Gray	Foliated
Marble		Light Colored	Unfoliated
Quartzite		Light Colored	Unfoliated
Slate		Dark Gray to Black	Foliated

Gneiss

Marble

Quartzite

Slate

GRANITES

Granite is endowed with a unique elegance. Throughout the centuries this stone has excited admiration for its beauty and time defying characteristics. Granite is a noble stone.

GROUP	Igneous
COMMON ROCK-FORMING MINERAL GROUP	Siliceous
COMPOSITION	Feldspar, quartz, and small amounts mica are the primary minerals of the average granite with minor accessory minerals.
HARDNESS	Hard	MOHS' SCALE	5 – 7
POROSITY %	0.4 - 1.5	ABSORPTION %	0.2 - 0.5
WEATHERING CHARACTERISTICS	Generally good to excellent. However, like any other material it has its vulnerable points...Some varieties contain ferrous mineral compounds that when continuously exposed to moisture, such as in marine coastal environments, will undergo mineralogical changes and being to produce discoloration's (rust spots)...In exterior applications, depending on the environmental conditions and the finish, darker granites, those with red and black minerals, have a tendency to fade somewhat
TENDENCIES	Absorbs oils and some will absorb other liquids...Generally not affected by acidic foods and drinks, however, polished granites can be etched by hydrofluoric acid and concentrated acids which are found in some household cleaning products...Some granite varieties when used in water features (spas and fountains), will begin to show signs of deterioration in a few years.
COLORS	Granite is found in more than a hundred distinct colors with varying patterns
FINISHES	Polished...Honed...Textured
NOTATIONS	When granite is used in the kitchen and bathroom it is highly recommended to treat the stone with a oil repellent...The grain size varies with this stone, from small, medium to coarse. This is important to understand for two reasons...1. With larger mineral grains or a combination of different grain sizes, the stone has a tendency to be more absorbent...2. Some varieties are composed with a combination of different grain sizes. This natural characteristic is more noticeable in highly polished finishes. The surface of the stone may appear to have tiny random pitting and a question that is often asked," is the finish of this granite defective in some way", and the answer is usually no. A real tight finish is not completely attainable with some of these varieties of granites. This characteristic is often not detected by viewing small samples of the stone...With textured exterior installations it is advisable to treat the stone with a water and soil repellent. Many of the texturing processes create and expose micro fractures in the stones surface increasing the absorption factor of the stone. * Contrary to popular opinion granite will stain.

True geological granite has been formed from molten material i.e. magma that cooled very slowly and crystallized deep below the earth's crust. This slow cooling, combined with the pressure from the overlying rock mass produced a well defined crystal structure and a very compact stone. Its name is derived from its granular texture.

The term "Granite" has taken on a broader commercial classification, referring to granite-type stones with similar characteristics, origins and having slightly different mineral compositions. The majority are geologically related to each coming from the same rock family. However some are far removed in their composition and their formation processes.

The trade term "Granite" has been incorporated in the names of some stones and this can prove to be misleading. For instance, Granito Nero is a black limestone, the name Belgian Granite is for a gray-black bituminous limestone, and Petit Granite is a black limestone. The name of a stone can become an important point in relation to what one thinks the stone is, just based on a name only and the intended use of the stone and it expectations

Granite

Granite

Granite

LIMESTONE

Limestone with its unique characteristics, subtle beauty and great versatility have made it a popular choice for any design style.

GROUP	Sedimentary
COMMON ROCK-FORMING MINERAL GROUP	Calcareous
COMPOSITION	Calcium Carbonate (Calcite) or the double carbonate of Calcium and Magnesium (Dolomite). Contains a variety of accessory minerals...silica, pyrite, iron oxides, clay minerals and bituminous matter from organic materials (plant & animals).
HARDNESS	Soft to Hard. Some varieties are as hard and dense as granite.		MOHS' SCALE	2 - 5
POROSITY %	0.6 - 31.0	ABSORPTION %	0.2 - 12.0
WEATHERING CHARACTERISTICS	Depends on the environmental conditions and the type of limestone...Exterior installation, in warm humid regions limestone weathers easily. If iron oxides or pyrite are present rust spots or runs may appear and if it contains bituminous matter dark blotchy spots or runs also may appear. Portuguese limestone's have been known to contain bituminous matter. Limestone surfaces in any climate may weather irregularly due to the mineral composition of the stone.
TENDENCIES	Absorbs oils and other liquids...Softer varieties have low scratch resistance. Acid sensitive as a rule. However, the Dolomite Limestone varieties are least affected...Some varieties have large pores while others have an open pitted textured surface capable of catching and holding dirt and soil.
COLORS	Range is in the pastel colors from white to creams through beige to pinkish...soft yellows through browns to rich crimson...medium green to dark blue-green...gray to black. Patterns vary from solid to variegated.
FINISHES	Any finish that is available is possible, depending on the variety...NOTE : Not all limestone's can be polished. As a general rule the lower the clay and silica content the better the limestone will take a polish.
NOTATIONS	Due to the high absorption factor of the majority of limestone's it is highly recommended for practical maintenance considerations and to minimize staining, that the stone be treated with a water and or oil repellent...It is important when choosing the treatment product that the solid content be carefully evaluated or a treatment product that has been specifically formulated for large pored stones be used. Some limestone's surfaces will roughen over time. This is not a form of decay, but merely the surface of the stone developing a natural patina.This is particularly true of Indiana and French limestone's.

Limestone is considered the most abundant chemical sedimentary rock. Many different types exist, yet the mineral composition of all limestone is similar. Most of them are of marine origin, formed in ancient warm shallow seas directly and indirectly from the life processes of marine plant and animal organisms. As these organisms died their calcareous remains, shells and skeletons accumulated in these sea beds building up vast deposits. Accompanying this process algae and other lime-secreting plants precipitated calcium carbonate in very fine clay to silt size particles which mixed with these fragments to form a calcareous ooze (mud). During these processes a wide variety of foreign materials ranging from clay minerals, quartz sand, iron oxides, and other minerals along with the remains of other plants and animals were being added to this sedimentary brew. As the waters receded these deposits consolidated to form limestone rock masses. In some limestone's the partial or complete fossilized remains of these extinct organisms can be seen.

Commercially those Limestone's that can be polished have been classified as a "Marble" and are sold as such. It can be very difficult to visually distinguish some of these limestone's from a true metamorphic marble.

White limestone

Limestone

Limestone

SANDSTONE

Sandstone has been a popular building stone for centuries. Its versatility and durable nature, with its variety of earth tones and textures makes it a popular stone used for paving, floors and much more.

GROUP	Sedimentary
COMMON ROCK-FORMING MINERAL GROUP	Siliceous
COMPOSITION	The main minerals are quartz, feldspar and mica with a variety of accessory minerals. These minerals may be cemented by silica, calcite or iron oxides.
HARDNESS	Medium to Hard	MOHS' SCALE	4 - 7.5
POROSITY %	0.5 - 35.0	ABSORPTION %	0.2 - 9.0
WEATHERING CHARACTERISTICS	The types of cementing material and the presence of silt or clayey matter will determine how well the sandstone will weather in any given environment. Those cemented by silica and have a high quartz content are extremely resistant...Iron oxide cemented sandstone's weather well in dry climates. They become harder and stronger, resisting weathering and deterioration. The calcite cemented sandstone's are more easily weathered. When silt and clayey matter are present they form poor bonds and absorb water easily, this can be a cause of flaking and spalling. Also in colder climates the absorbed water freezes resulting in cracks and spalling. The surface of some sandstone's may not weather uniformly, there may be a lose of material by flaking, spalling, etc. in some areas and not in others because sandstone is formed in layers. Some of these layers may be more resistant due to their composition and if the surface is cleft, different layers are exposed all resulting in a differential weathering process.
TENDENCIES	Absorbs oils and other liquids easily.
COLORS	White to buff...Full range of earth tones to multi-colored banded pastels.
FINISHES	Natural Cleft Texture...Honed...The harder denser varieties will take a High Honed Finish.
NOTATIONS	Due to the high absorption factor it is highly recommended for practical maintenance considerations and to minimize staining, that the stone be treated with a water/soil and or oil repellent.

Sandstone is predominantly composed of consolidated quartz sand grains cemented together. They come from three primary formative environments, ancient shallow sea beds, fresh water rivers and deserts. There are different varieties of sandstone's, generally defined as "calcareous", the cementing agent being calcite, "quartzitic", high quartz content cemented by silica also referred to as a "quartzite", this is a sedimentary rock and not to be confused with a "metamorphic quartzite", and "arkosic", containing quartz and a notable quantity of the mineral feldspar, the cementing material is usually calcite or iron oxide.

Sandstone

Sandstone

Sandstone

SLATE

Slate with its natural colors, varied multicolored patterns and textures provide this stone with a distinctive appearance.

GROUP	Metamorphic
COMMON ROCK-FORMING MINERAL GROUP	Silicates
COMPOSITION	Muscovite, chlorite, kaolinite, micas, quartz and other accessory minerals (wide variation in composition)
HARDNESS	Soft to as Hard and dense as granite	MOHS' SCALE	2.5 - 5.5
POROSITY %	0.4 - 5	ABSORPTION %	0.1 - 1.7
WEATHERING CHARACTERISTICS	Do to the wide ranges of slate, this stone has wide ranges of weathering. Cleft planes provides permeability for water penetration resulting in spalling and flaking. Slates that have a high kaolinite content (a clay) display accelerated rate of deterioration in wet environments.
TENDENCIES	Absorbs oils and liquids...Softer/medium varieties scratches easily.
COLORS	Colors very widely.
FINISHES	Natural Cleft...Honed...Some types my be Flamed.
NOTATIONS	Sealing to minimize staining...Colored slates benefit from color enhancing treatments designed to magnify and protect the natural colors. When dealing with colored slates there are two distinct types, Fading and Unfading. After a period of exposure to the environment (sun/water) fading slates will alter generally to a lighter color. The unfading varieties will retain their true colors. Multi-colored slates used for flooring will undergo color changes in abrasive foot-traffic areas. The colors in these varieties of slates are in thin bedded layers...Some slates will dust for awhile after installation on floors as loose scale is removed by foot traffic. This will stop as the surface settles in, usually in a few weeks...*The majority of the multi-colored slates are what are termed "clay slates" and generally have a high content of clay minerals and are geologically classed as a low-ranked slates, those in which the metamorphic process was halted at a very early stage. These slates weather poorly in exterior wet/humid climates.

Slate is a fine grained metamorphic stone formed from clay mud; composed of sediments of decomposed stone and organic matter that has been hardened by heat and pressure. Since the geological process varies greatly, slates range quite a bit in hardness and porosity.

Commercially "Slate" has become a trade term. This has lead to the classifying of some stone types as slate. An example of this is using "Shale" that's been commercially classified as "slate", (most slates where a shale before the metamorphic process). Shale weathers poorly and very poorly in wet/humid climates. Soon after installation in exterior applications this stone crumbles, spalls excessively and can literally turn to power.

It's important to judge the performance characteristics of different slates individually and not assume that all slates are alike.

Slate

Slate

Slate

MARBLE

Marble is a beautiful and exciting material with its varieties of veining, patterns and its palette of colors; this stone communicates permanence, integrity, quality and elegance.

GROUP	Metamorphic
COMMON ROCK-FORMING MINERAL GROUP	Calcareous
COMPOSITION	Calcite, dolomite or a combination of both and accessory minerals acting as coloring agents. Veining minerals range from calcite, quartz and a variety of other minerals.
HARDNESS	Soft to Hard...Generally Soft to Medium		MOHS' SCALE	3 - 5.5
POROSITY %	0.5 - 2.0	ABSORPTION %	0.2 - 0.6
WEATHERING CHARACTERISTICS	Moisture sensitive as a rule. All polished marble will lose their polish in exterior applications.
TENDENCIES	Absorbs oils and other liquids...Easily scratched...Acid sensitive.
COLORS	Every color is possible due to the variability of accessory minerals.
FINISHES	Honed...Polished
NOTATIONS	Some marbles are more moisture sensitive than others, Creme Marfil, Perlino Rosata, Bottiocins, Breccias some Perlatos and Rosa Veronas, and some are extremely moisture sensitive, as a rule the red, black and green marbles. This color group of marbles may present problems such as warping, blistering,and spalling when installed with setting materials containing water. It is strongly recommended that the use of a water free epoxy adhesive be used with black and green marbles. Marble used in the kitchen should be carefully evaluated due to its acid sensitivity. Treating marble with a water or oil repellent is highly recommended.

Marble is a metamorphic stone. It was at one time a limestone or dolomite that has been structurally altered by recrystallization. Pure marble is white. The abstract variety of colors, mottling, clouds, swirls, shadings, streaks and veining are derived from the accessory minerals that were present in the limestone or dolomite.

Commercially "Marble" has become a trade term, which is used o classify a wide rage of stones used for decorative purposes that are capable of taking a polish. Those stones that are grouped into this commercial classification are geological marbles and limestone's that can take a polish, also dolomites, travertine's, onyx and serpentines (green marbles).

Marble like any other building material has its strengths and limitations. It is important to judge the performance characteristics of different stones individually and not assume that all marbles are alike.

Marble

Marble

Marble

The Different Forms in Which Stones are Used

The construction industry uses stones in the following forms:

·         Fieldstone – rough stones obtained from river beds and fields.

·         Rubble – irregular quarried fragments that have at least one good face.

·         Dimension stone- quarried and cut into rectangle form.

·         Cut stone- quarried and cut into large slabs.

·         Ashlar – small rectangular blocks.

·         Flagstone – thin slabs of stone; either regular or irregular shape, used for flooring and paving.

·         Crushed stone – useful in site work as freely draining fill material, pavings, surfacing materials and aggregates.

USES OF STONE IN BUILDING INDUSTRY

Type of stone	Minerals	Area of use
Clay slate	Clay mineral	Roof covering roof ; flooring
Diabase	Plagioclase ; Pyroxene	Rockwool : crushedas aggregate in concretes ; structures
Gabbro	Feldspar ; Pyroxene	Crushed as aggregate in concretes ; structures ; flooring ; wall cladding
Gneiss	Aluminium silicates ; Quartz ; Mica	Crushed as aggregate in concretes ; structures ; flooring ; wall cladding
Granite	Feldspar ; Quartz ; Mica	Crushed as aggregate in concretes ; structures ; flooring ; wall cladding
Limestone	Lime	Ground to limeflour (cement , lime binder , ect.) ; smaller structures
Marble	Lime / Dolomite	Structures above ground ; flooring ; cladding
Mica slate	Quartz ; Feldspar ; Mica	Roof covering ; wall cladding ; flooring
Phyllite slate	Quartz ; Feldspar ; Mica	Roof covering ; wall cladding ; flooring
Sandstone / quartzite	Quartz ; often inci ; lime or feldspar	As sand (production of Portland cement , concretes , fillers) ; smaller structures
Serpentine	Serpentine mineral ; Chlorite ; Magnesite	Cladding , flooring
Steatite / soapstone	Talc ; Chlorite ;Magnesite	Structures above ground ; cladding
Syenite	Aluminium silicates ; Pyroxene	Crushed as aggregate in concrete ; structures ; flooring ; wall cladding
Quartzite slate	Quartz ; Aluminium silicates ; Mica	Roof covering ; wall cladding ; flooring