Stone and Tile Definitions

Below you will find definitions of common natural stones that we use to produce our floor medallions. The common designation for any natural stone that takes a polish is ‘Marble’. Marbles may be further segregated into the following.

Granite

Granite is a light-colored igneous, or volcanic rock, with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth’s surface.

Granite is very hard and extremely durable. It has a very grainy structure and can be polished well. This type of stone comes in a variety of colors ranging from salt and pepper to reddish brown to jet-black.

Granite is composed mainly of Quartz (35%), Feldspar (45%) and Potassium with minor amounts of mica, amphiboles, and other minerals.  Granite is the best-known igneous rock. Many people recognize granite because it is the most common igneous rock found at Earth’s surface and because granite is used to make many objects that we encounter in daily life.

Granite contains very little calcite, if any.  It is very hard material and easier to maintain than marble. Yet it is still porous, it will stain, and is much harder to remove scratches if they occur. 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. Granite is a wise choice for heavy traffic floor medallions.

Marble

Marble is a metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed primarily of the mineral calcite (CaCO3) and usually contains other minerals, such as clay minerals, micas, quartz, pyrite, iron oxides, and graphite. Under the conditions of metamorphism, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. A related rock, dolomitic marble, is produced when dolostone is subjected to heat and pressure.

Most marble forms at convergent plate boundaries where large areas of Earth’s crust are exposed to regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone.

 

Travertine

Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material.

Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate minerals from solution in ground and surface waters, and/or geothermally heated hot-springs Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa.

Limestone

Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal, and fecal debris. It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water.  Most limestones form in shallow, calm, warm marine waters.

Some dense limestone can be polished. Common colors are black, grey, white, yellow or brown. It is more likely to stain than marble.

Slate

Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism. It is popular for a wide variety of uses such as roofing, flooring, and flagging because of its durability and attractive appearance.

Slate is composed mainly of clay minerals or micas, depending upon the degree of metamorphism to which it has been subjected. The original clay minerals in shale alter to micas with increasing levels of heat and pressure. Slate can also contain abundant quartz and small amounts of feldspar, calcite, pyrite, hematite, and other minerals.

Most slates are gray in color and range in a continuum of shades from light to dark gray. Slate also occurs in shades of green, red, black, purple, and brown. The color of slate is often determined by the amount and type of iron and organic material that are present in the rock.

Quartzite

Quartzite is a nonfoliated metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together. The result is a network of interlocking quartz grains of incredible strength.

The interlocking crystalline structure of quartzite makes it a hard, tough, durable rock. It is so tough that it breaks through the quartz grains rather than breaking along the boundaries between them. This is a characteristic that separates true quartzite from sandstone.

Quartzite is usually white to gray in color. Some rock units that are stained by iron can be pink, red, or purple. Other impurities can cause quartzite to be yellow, orange, brown, green, or blue.

The quartz content of quartzite gives it a hardness of about seven on the Mohs Hardness Scale. Its extreme toughness made it a favorite rock for use as an impact tool by early people. Its conchoidal fracture allowed it to be shaped into large cutting tools such as ax heads and scrapers. Its coarse texture made it less suitable for producing tools with fine edges such as knife blades and projectile points.

 

Ceramic/Porcelain

Porcelain and ceramic tiles are man-made products.  Both are made of clay that has been fired in a kiln.  Porcelain tiles are commonly used to cover floors and walls, with a water absorption rate of less than 0.5 percent. The clay used to build porcelain tiles is generally denser.

Ceramic tile is similar to porcelain tile, and while some companies use the terms interchangeably, they are actually very different. Ceramic tile is not as dense and has a higher absorption rate. This means that it is not frost-proof, and it may chip or damage more easily than porcelain tile. Despite these differences, ceramic tile is a very popular choice for floors, counter-tops and walls.

Note: Granite, Marble, and Natural Stones are a product of nature and therefore will vary in color, veining, surface texture, fissures and naturally occurring cracks.