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History of Stone:

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     Granite stone is hewn from the earth and is extremely dense yet also porous. Once it is cut and polished it must be sealed to prevent stains. Its very permanence makes it difficult to work and shape, but technological advances have made it possible to cut and polish stone near quarries around the world, a money-saving development that enables unusable pieces to be discovered before they are shipped abroad.

    Granite is cut with diamond saws, then polished like glass and shipped around the world where it becomes the most cosmopolitan of counters. It exists everywhere in the world, yet nowhere is it the same. Even from the same quarry, no two pieces are identical.

    Granite, the most popular stone for counters, is an extremely hard rock formed by volcanic activity. Its shimmering beauty lies in the crystals of quartz, mica, and feldspar trapped within. So-called consistent granite has the same pattern throughout. Variegated granite has veins that vary from piece to piece, which add character but also it difficult to match sections.

    Soapstone and slate are much softer than granite but also less porous. Slate was formed from clay on ancient sea beds and generally has a solid gray, black, or green hue. Soapstone, which is composed primarily of the mineral talc, has a similar color but often contains light striations of quartz. Both stones scratch and chip easily, especially on the edges; the marks can be sanded out or left to add character. Combined with a sink of the same material, slate or soapstone counters can create a classic farmhouse look or a sleek, refined look. It's not generally necessary to seal these stones, but a periodic application of mineral oil will make them glow.

    Marble and limestone are warm and soft but less practical for kitchens because food acids stain them readily. Still, many homeowners don't mind stains that add a patina of age. And marble is a classic surface for rolling out pastry; serious bakers often include a section of marble countertop in their kitchens for this purpose. Marble is generally polished like granite; limestone is often honed to a matte finish.
 

What Is Granite:

Granite - Earth’s Oldest Building Material

    Granite is—quite literally—as old as the earth. It is formed from liquid magma, the molten rock still found at the core of the planet, cooled slowly to form a substance approaching the hardness and durability of diamond. Granite is an igneous rock, the name reflecting its fiery beginnings. The chemical composition of granite is similar to that of lava. However, granite owes its hardness and density to the fact that it has been solidified deep within the earth, under extreme pressure. Over the eons, seismic activity has changed the crust of the planet, forcing veins of granite to the surface. Glaciers scraped off layers of dirt, sand and rock to expose granite formations. Typically revealed by outcrops, the deposits have been discovered on all the continents.

Composition

    It is accurate to speak of "granites," because many varieties of the stone exist. While they differ in color, texture and crystalline structure, the granites have three essential minerals in common: Feldspar, Quartz, and Mica.
These minerals occur in different proportions, giving each granite slab its own color, texture and structural characteristics. In addition, hornblende, magnetite, hematite, pyrite, zircon, garnet, corundum and other minerals may be present in smaller amounts, adding to the unique coloration and texture of each granite deposit. In supplying granite for a large building or complex of buildings, it is essential that the stone be consistent in color and texture. To assure this, each granite color must be quarried from the same deposit. With natural material like granite, a certain amount of "movement" or grain in the stone must be expected. Many people find this flow and blending of colors to be the most compelling reason for using granite.
 

 

Physical Properties of Building Stone:

Expansion – Weathering - Permeability

    All stones are natural materials subject to variation in properties according to specific mineral composition, size and thickness of the tested piece.

Coefficient of Expansion

    Stone expands and contracts minimally with temperature change. Normally the amount of change is too insignificant to cause a problem. However, some of the purest marbles retain a small incremental change after each heating cycle. This is called hysteresis. In thin veneers, it can put strain on the backing material and cause bowing and even rupture. This also increases the porosity of the stone, making it more susceptible to attack from atmospheric acids and cyclic freezing. In granite and limestone, the amount of change is in millionths of an inch—usually not enough to cause problems. In some marbles and sandstones, the coefficient is in hundred-thousandths of an inch, which could cause problems. In most construction systems, the normal fasteners and joint materials accommodate minor expansion and contraction of the stone.

Weathering

    Stone generally weathers better than other building materials; however, not all stone endures equally well. Some are subject to greater damage from freezing and thawing and attack from sulfurous and sulfuric acid, carbonic acid and ammonium salts. Granite is nearly impervious to weathering from temperature changes and from airborne chemicals. In fact, granite is so resistant to chemical erosion that granite tanks are often used to store highly caustic materials.
Freeze/thaw weathering rarely occurs in polished granite surfaces. Weather damage to granite with any finish is extremely uncommon because of its inherently low absorption rate.

Permeability

    Granite is significantly less porous than other building stones, yet it is capable of absorbing moisture. Fabrication is a "wet" process: the cutting of granite is accomplished with a slurry of water and abrasive material. Sometimes granite is shipped before it is completely dried, and the moisture absorbed during fabrication gives the granite a different color than in its dry state. Such stones will dry in relatively short order and return to their true color. Once dry, the atmospheric moisture precipitation and humidity will not normally penetrate the stone.

Variegation

    Granite is very consistent in color and texture when compared to marble; however, granite also exhibits movement and color variation.
 

 

Comparing Granite To Other Building Materials:

All Stone Is Not The Same...

    There are several different types of building stone on the current market. At The Granite Gallery, they include common stone such as granite, marble, limestone, travertine, as well as the man-made CaesarStone™. Each stone has unique physical characteristics, which affect its applicability to various building designs. This section describes the characteristics and physical properties of the major building stones.

Granite

    Granite is an igneous rock created deep within the earth from magma, cooled slowly under great pressure. It is the hardest building stone with very dense grain, making it virtually impervious to stain. It takes a highly polished finish, which will endure even in inclement environments. It also can be finished in a variety of other ways. There is a broad spectrum of granite colors ranging from nearly pure white to nearly pure black. During its formation, granite may also have been infused with other minerals providing patterned "movement" as well as color.

    Most common uses: Interior and exterior wall cladding, interior and exterior paving, residential & commercial counter tops, monuments, curbing, statuary, balance tables, novelty items, etc.

Marble

    Marble is a metamorphic rock, composed of metamorphosized limestone. In its purest form, marble is crystalline white calcite. Most marbles, however, are infused with impurities such as dolomite, silica or clay, providing variations in color and significant movement. The base colors of marble range from white to black with a broad range of hues. Marble is significantly softer than granite and therefore subject to greater wear and weathering.
Most common uses: Interior and exterior wall cladding, Interior and exterior paving, Fireplace facing and hearth, Lavatory tops, Residential & Commercial counter tops, Table Tops, Statuary, Novelty items, Many non architectural uses, such as tooth paste, paint whiting, agricultural lime, etc.

Limestone

    Limestone is a sedimentary rock composed of calcites and dolomites. Organic limestones were formed from the deposits of marine shellfish and fossils. Limestone is non-crystalline and possesses very uniform composition, texture and structure. It is soft and therefore easy to quarry and shape. Limestone ranges in color from white to gray and does not take a polish.
Most common uses: Interior and exterior wall cladding, interior and exterior paving, limited counter top use.

Engineered Stone

    Most engineered stone is a quartz aggregate bound with a polyester resin. It is very hard but there are question in the industry about the absorption of liquids over time.
Most common uses: Kitchen countertops & backsplash, bath vanity tops, tabletops, fireplace surround.
 


 

 

 

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Last modified: 06/03/09