As with granite, marble is used as a general term to describe an array of similar dimensional stone. Marble is a timeless classic used throughout history because of its softer composition and ease to work with. The majority of marble in the world comes from India, China, Italy and Spain.
Marble is a metamorphic rock and is usually is a transformation from limestone. As limestone (a sedimentary stone) gets pushed further into the earth from the surface, the stone begins to get heated from the core. As the pressure and heat builds, it creates a chemical process that alters the mineralogy, texture and chemical composition of the stone, it really goes through a metamorphosis!! There are two different types of metamorphic rock, 1) foliate; which consist of harder stones such as gneiss, schist and slate (these stones sometimes are grouped with the consumer term “granite”). 2) non-foliate; these are the common marble and quartzite. Foliate stones generally have a layered or banded look to them which non-foliate stones do not.
While granite is grouped into the siliceous group, marble is grouped in the calcareous group as most marbles are composed primarily of calcium carbonate (in the form of calcite or aragonite). Calcareous stones are susceptible to acid attacks and are softer than siliceous materials. In the Mohs Scale of Hardness, calcite is ranked only a 3 out of 10, your finger nail is ranked at a 2.5!
Limestone and travertine are both sedimentary stones that are formed by deposits of minerals at the earths surface (usually in water). These materials are formed literally from sediments “settling” on each other. These types of stones are very popular for their soft earth tones and its neutral color palette with allows for integration of a variety of colors and textures. Travertine is an especially popular floor and wall tile. These stones are also popular (especially limestone) for the presence of fossils within the stone.
Limestone & travertine are composed primarily of calcium carbonate and, like marble, belong to the calcareous group. This means that they are also susceptible to damage from acids and they are softer than granite. Travertine is a type of limestone that is created in special conditions during the deposition of the minerals. This creates a stone area that has immense voids like air pockets in the stone that requires filling with a grout or other type of filler when the stone is finished.