MARBLE

CALCITE

 (CaCO3)

Calcite, the dominant mineral of marble, is extremely common and found throughout the world in sedimentarymetamorphic, and igneous rocks. Some geologists consider it to be a "ubiquitous mineral" - one that is found everywhere. They serve as one of the largest carbon repositories on our planet. The properties of calcite make it one of the most widely used minerals, ranging from construction, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical and more. It has more uses than almost any other mineral. Many of the desirable qualities and many of the problems commonly encountered with marble are direct consequences of the properties of calcite, the dominant mineral. A review of the physical and chemical properties of calcite follows:

SCRATCH RESISTANCE

The hardness and uniform wearing qualities of most marble varieties make them extremely desirable and economically practical for floors and walls. Kitchen countertops however might be a more demanding surface and therefore it is important to keep in mind that when marbles is applied in countertops simple steps should be taken like avoid cutting food directly on the stone (it is recommended to use a wooden cutting board for that, even in granite and quartzite countertops). 

STAIN RESISTANCE

Contrary to popular belief, marble is not a very porous stone. However, if given enough time liquids might penetrate the pours of the stone and once it penetrates a stain can occur following the evaporation of the liquid. The good news is that for the past few years the stone industry came up with several treatments to seal and impregnate the natural pours of the marble surface. These sealers and impregnators are made up of a liquid based solvent (typically water based) and a solid resin. The solvent is the carrier that penetrates the pours in the stone surface and then evaporates leaving behind the solid resin that plugs the marble's pours and prevent foreign substances from penetrating the surface thus preventing stains. Marble Sealers do a great job at preventing stains, but it is important to note that no sealer is perfect and if liquids are given enough time they can still penetrate and leave stains. So when you apply your sealer it's important not to forget about cleaning and caring for your marble. 

FIRE RESISTANCE

Marble is not combustible and therefore is considered a fire-resistant material. Because of its thermal conductivity, heat transfer is fairly rapid. Most stone is not considered a highly rated thermal insulator.

UV RESISTANCE

TCalcite, the dominant mineral of marble, occurs in many colors. Among the many common trace-amount impurities that color marbles are organic matter (generally gray to black), chlorite (generally light green to yellowish-green), epidote (the same green as above), and minor amounts of land-derived clays, silts, and sands. These clastic silicate sediments may already be stained with iron to yield any color from very light buff to dark brown, and almost any red color; or the silicate grains themselves may contain trace amounts of iron available by chemical release to stain and color. Other known coloring agents are too numerous to mention here. Iron is by far the most common.

FOOD SAFE

Bacteria requires several things in order to thrive and grow: oxygen, water, sunlight, nutrients, and a substrate to form on. Marble tile and slabs are double sealed before being polished and this treatment prevents bacteria growth. If an extra layer of protection is needed, marble slabs may also be processed with bacteriostatic resin which utilizes a US EPA registered antimicrobial product.

TRANSLUCENCE

 

The translucency of marble is one of its most intriguing attributes. Translucence is dependent on the following factors:

a) Crystal Structure: Marbles of certain crystal structure are especially adaptable to transmitting light.

b) Color: The white and lighter- colored marbles are generally more translucent.
c) Thickness: The light transmission diminishes as panel thickness increases.

d) Surface Finish: Translucency is more apparent in smooth finishes than in rough finishes.

Source: Dimension Stone Design Manual, Version VIII (May 2016)

 

Marble is the most noble of the natural stones. The word Marble derives from the an ancient Greek word that means "shining stone"  and it is a cultural symbol of tradition and refined work. 

Marble is geologically defined as a metamorphic rock consisting of fine grained, recrystallized Calcite (CaCO3). In other words, marble is formed when an original stone (limestone) is subjected to enough heat and pressure to changed it (metamorphose) into a new stone. The size of the calcite crystals is determined by the level of metamorphism: marble that has been subjected to higher levels of metamorphism will generally have larger calcite crystals. Due to these high pressures of metamorphism, it is expected marble to be tighter, denser, and more fracture-free than other kinds of stone.

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