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Granite? Marble? Soapstone? What does it mean? The lowdown on natural stone types.

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Granite? Marble? Soapstone? What does it mean? The lowdown on natural stone types.

Granite

An excellent choice for kitchen countertops, floors, and other heavily used surfaces

blue pearl granite

Blue Pearl

Exact and current extraction figures are not available, as data collection from many countries is difficult. Statistics from various sources indicate that the granite quarried in the countries of China, India, and Brazil comprises approximately 2/3 of the granite used worldwide. There are granite quarries in operation in dozens of countries, and it is one of the most popular natural stones on the market. New granite resources are continually being located and developed throughout the world.

Granite has long enjoyed use as an exterior cladding and pavement material, and its inherent strength, abrasion resistance and superior weathering durability are likely to keep it one of the preeminent material selections available to today’s architects. Granite has also been employed as the traditional material for municipal curbs, where its strength and durability have been documented with decades of vehicular abuse. In the northern climates where snow melting chemicals are used heavily, granite has resisted the attack of these caustic agents.

Being one of the hardest of the dimension stone types, granite was historically avoided by the smaller, local stone fabricating shops, who favored marbles and limestones due to their easier working properties. A recent boom in the supply of affordable machinery and abrasives technologies eliminated these previous difficulties in fabrication. The use of granite has skyrocketed in residential interior applications as a result. Available in a striking array of colors, granite’s durability, longevity, and economy make it ideal for kitchen countertops and other heavily used surfaces, including table tops and floors.

Some synthetic surfaces scratch easily, while the hardness of the minerals comprising most granites surpasses that of the utensils that are used on them, resulting in excellent scratch resistance. Granite is typically heat resistant up to temperatures of ±250°C (±480°F), although direct application of localized heat sources is discouraged, since strong thermal gradients within the stone can initiate cracking. Studies of bacteria retention on common countertop surfaces have proven granite to be superior to the majority of surfaces employed for that purposes (Ref: MIA Technical Bulletins).

Absorption rates (% water, by weight) of stones in this group range from 0.05% to 0.40%, indicating that the available pore volume capable of harboring a staining agent is very slight. Impregnating repellents are sometimes used to further increase the stain resistance of these materials.

 

Marble, Onyx, & Serpentine

Ideal for foyers, bathrooms, floors and hearths

marble stone

Marble Stone

Marble is a metamorphic rock found in the mountainous regions of most countries of the world. Marble quarried in India, China, Italy, and Spain represents the majority of marble, in terms of volume, that is utilized worldwide. Because of its beauty and elegance, marble is a popular choice for countertops, floors, foyers, fireplace facings and hearths, walls, and windowsills.

Marble with its inherent warmth, adds a sophisticated element to the area in which it is installed. Its naturally random appearance, engineering characteristics, and ease of maintenance makes it a premium choice for floors, wall claddings, table tops, wainscot, floors, and vanity tops. Many marbles are well suited for wet area application, which extends the versatility of this material to include tub decks and showers.

The calcite crystal is the basic building block of true marbles. The calcite crystal is vulnerable to attack by mild acids, including those commonly found in kitchen and bar settings. The user selecting marble for these applications should be aware of, and accepting of the maintenance and patina that is to be anticipated with this combination. Acid rain and other weathering elements can also affect exterior marble installations, and exterior applications are generally limited to white marbles, with some exceptions.

Often mistaken for marble is serpentine, which is actually magnesium-silicate based as opposed to calcite based. As a result of the different mineralogy and whole rock chemistry of serpentine, it exhibits greater acid resistance and abrasion resistance than does a true marble. These properties make serpentine a common choice for both kitchen counter and exterior application.

Onyx is often confused with marbles, yet it is a significantly different rock type. Onyx is a sedimentary rock, formed as stalactites and stalagmites in cave interiors. This formation method results in the cryptocrystalline construction of the rock fabric, and it is the size and uniformity of these crystals that contribute to the classic translucent property of most onyx varieties. While vulnerable to chemical and abrasive attack, the decorative appeal of onyx is perhaps unsurpassed by any other material.

 

Sandstone and Quartzite

Exploring the “quartz-based” stones

quartzite

Quartzite

The term sandstone refers to the sand sized (0.06 to 2.0 mm) clasts that are cemented together by other agents. Therefore, sandstone could be of any mineralogy, but the overwhelming majority of sandstones on the market are quartz-based.

The durability and performance of sandstone is not as greatly influenced by the sand sized particles, as it is influenced by the cementing agent that binds these particles together. Many types of sandstone are used in cubic sections as sills, coping, watertables and other exterior features. Exterior cladding is also a common application, although this stone variety is typically used in thicker sections than other stone types due to lower bending strengths. While sandstone has been used in both countertop and shower lining applications, the varieties that are suitable for these installations are limited.

Quartzite is a metamorphic rock that is formed from sandstone. Quartzite can be of exceptional strength, density, and hardness. The strength, abrasion resistance, and weathering durability of this rock type expand its application possibilities to include most any of the common uses for natural, dimension stone.

 Slate and Soapstone

Versatile, Chemically Resistant Materials

soapstone

Soapstone

A traditional use of both these materials was the laboratory table top in chemistry labs. That application alone should serve as a great testimonial to the chemical resistance of the materials.

Being of the softer varieties of dimension stone types, neither of these materials is known for particularly high abrasion or scratch resistance, yet they are both used a flooring and countertop products.

Soapstone is highly heat resistant, and has been used in fireplace surrounds frequently to take advantage of this property.

Slate, being of laminar construction, has the ability to be processed into thin sheets and still maintain serviceable strength and rigidity. This property makes slate the only dimension stone having been used for blackboards and roofing shingles. It was also traditionally used as the cloth-covered playing surface of billiards tables.


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