Marble is sedimentary rock, its name derives from Greek and means "shining stone". There are endless colour variations, due to different crystallisation over the millennia and to the type of impurities in the stone (clay, silt etc ).
Due to its preciousness it is mainly used in construction for indoor and outdoor facing and flooring in the form of slabs, and not as structural building material. Besides, it is easily stained by some types of acid such as lemon or vinegar and needs a certain amount of specialised maintenance.
Carrara white marble is perhaps one of the most widely known in Italy.
The word marble comes from the ancient Greek marmairon, meaning "to shine" which referred to rocks that could be polished. The origin of the term is associated to the fine white Proconnesian marble from the island of Marmara in the sea of the same name, one of the first ancient materials to be cut into slabs and exported to Pompeii, Rome and along the Danube, as well as the first stone to be used to construct Constantinople.
The Romans also used the same term "marmora" to refer to all stones (lapis) that could be polished, be they granite or marble, whereas Lapides were those that could only be smoothed, like tuff and travertine. The Romans would generally import stone (lapis) typically used by the peoples they conquered such as porphyry, granite and alabaster from Egypt, marble from Anatolia, Cipollino Mandolato from the Pyrenees, Breccia Verde of Sparta or yellow marble of Numidia (Tunisia) to symbolise the conquered territory in altars and temples to their gods, as if to metaphorically gather many different realities in the same place.
These materials are called Ancient Marble and are the object of extensive study by the Fine Arts, although for some of them the quarrying place is still unknown.
The empire later started quarrying the closer white Carrara marble, seeking cheaper alternatives to Greek white marble, as transport was by sea, then as now, and expensive.
However, the building materials (lapides) were local stone sourced from time to time for their closeness and ease of processing, such as Travertine for Rome and Ceppo for Milan.
White marble is the purest, from 99% calcite of Carrara White Statuary to 90% of Cipollini Apuani nearby. The veins are amorphous structure impurities. Among the features of Carrara Statuary - a material so dear to Michelangelo - fine grain is as important as purity, as it assures more detailed working. In fact, the finer the marble grain the greater the use in sculpture. Pure, crystalline marble is white, all other colours are impurities. For instance, red marble is often the product of iron oxides. With increased impurities the molecular structure is increasingly amorphous (disarrayed).
According to standard EN 12670 however, marble is defined as metamorphic rock with carbonate content higher than 50% and includes other types of rocks such as breccia, which is recent rock originating as agglomerates of older stones combined in a matrix of natural cement or non-metamorphosed sedimentary rocks.
Rosso Verona and all stones where fossils can be identified are not marble as they are sedimentary.