What is limestone?
Limestone is a sedimentary rock composed largely of calcium carbonate (CaCO3). It is formed by the accumulation of shells and skeletons of marine animals on the ocean floor. This process began millions of years ago at a time when the surface area and volume of the oceans were much larger. Limestone can be found in canyons and cliffs where large bodies of water have receded, revealing the layered rockface. It is the most common stone surrounding the Mediterranean basin in France, Spain, Italy, Turkey, Israel, and Egypt.
Limestone is generally recognizable by the presence of fossils and is available in a variety of neutral colors. These range from cream, beige, and gold to grey, blue, and black.
GRAND CANYON, ARIZONA
What is Marble?
Marble is a metamorphic rock resulting from regional or contact metamorphism of sedimentary carbonate rocks, i.e. limestone. This metamorphic process causes a complete re-crystallization of the original stone into an interlocking mosaic of calcite and dolomite crystals. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original material. Geologists use the term “marble” to refer to metamorphosed limestone.
Marble is usually identified by its contrasting vein patterning. The purest calcite marble is white, but the presence of other minerals can change the color to more vibrant tones including reds, yellows, and greens.
CARRARA MARBLE QUARRY, ITALY
CREMA MARFIL QUARRY, SPAIN
What is travertine?
Travertine is a form of limestone deposited by mineral springs, especially hot springs. It is formed by the rapid precipitation of calcium carbonate in locations with more water turbulence like the sources of streams or small waterfalls. Small cavities called vacuoles are formed by the bubbling of carbon dioxide evasion while the minerals are settling. This gives travertine its natural holes and cloudy patterning.
When pure, travertine is white in color, but most often the dominant colors tend toward earth tones of gray, cream, tan, gold, rust or brown, depending on the type of impurities present.
TRAVERTINE POOLS, TURKEY
TRAVERTINE POOLS, TIBET
What is Basalt?
The oldest type of all rocks is the igneous rock. Deep inside the earth, the temperature is very high and the minerals there are in liquid form called magma. As the magma pushes towards the earth’s surface, it starts to cool and turns into solid igneous rock.
All igneous rocks do not cool the same way. Intrusive igneous rocks cool slowly, deep under the earth’s surface and form with large crystals, like Granite.
Extrusive igneous rocks form above the surface of the earth when magma erupts from a volcano or reaches the surface through large cracks. Once it reaches the earth’s surface it cools quickly and forms rocks with small crystals. Basalt is an example of this type of rock. It is generally very consistent in color and is found in shades of grey or black.
DEVIL’S POSTPILE, CALIFORNIA
BASALT ROCK, VIETNAM
What Are The Visual Differences Between These Stones?
Limestone, marble, and travertine have the same chemical properties, but they have different physical properties. They are all sensitive to acid, unlike granite and basalt, yet they vary greatly in density and porosity.
Limestone is the only stone where fossils are the most obvious visible feature. Marble is identified more by the prominence of veining. Travertine on the other hand has a cloudlike movement in its patterning as well as small cavities that can be left naturally open or filled. Basalt is more consistent overall in color with very little movement or patterning.