How did marble come about?

Answer

Marble is a beautiful natural stone, suitable for decorative use indoors or in sheltered places, with the following properties: suitable for polishing (where marble becomes smooth in surface, acquires a shine and seems to come to life), and not abrasive (without abrasive grains); marble is also composed of the mineral calcite (calcium carbonate).

Marble is thus used as a decorative floor tile, for cladding shop fronts but especially palaces, cladding fireplaces, table tops, sculptures, etc. It is affected by acid rain, kitchen acids, and easily scratched by sand, knives or other hard materials.

For the origin of marble we come to geology and then it appears that there are 2 types. Firstly, sedimentary marble that arises as lime deposits in the biosphere (due to precipitation of lime mud and fossils) which must then be completely petrified, by being buried under hundreds of meters of this set of overlying rocks (marble is usually called a respectable age) where the following properties are important:

• there should be no cavities (marble should not absorb water)
• there should be no cracks or tears (because then it will not be polished to final shape)
• it should not contain any pebbles or resistant minerals (because then the marble cannot get its smooth surface and shine)
• there may be a little clay or impurity in it, good for the color and color shades, but not too much because then the marble is not compact enough

All these quality requirements are very strict because marble does not so much stand for a species but mainly for a quality of rock. The traditional black, gray and red Belgian marbles belong to this group of sedimentary marble-like rocks.

Furthermore, there is a second group of metamorphic marbles. The limestone (regardless of whether it was of marble quality) was brought under high pressure and temperature kilometers deep in the earth’s crust through mountain formation processes, where metamorphism occurs: the rock starts to recrystallize.

A metamorphic marble usually shows slightly coarser sugary crystals of the mineral calcite. The ideal example is white marble, in which Michelangelo, for example, sculpted his statues. Due to impurities, the metamorphic marble can also tend towards beige, green and red or vaguely show these shades. Some geologists consider the metamorphic marbles to be the only true marbles. They come mainly from the Mediterranean. There are other marble-like rocks that are often also described as marble in the natural stone trade, for example green serpentinite, a highly metamorphic rock that is formed by metamorphism from an earlier ocean floor.