Stone is catergorized into three parts
- Igneous, which most better known as Granite but also in this category is Quartz, Obsidian and Pumas.
- Sedimentary, which are limestone, travertine, Sandstone, Gypsum and Conglomerate
- Metamorphic, which are Slate and Marble
Marble belongs to the metamorphic family. Commercially, any kind of calcareous and sepentine-based dimensional stone which can be polished would be classified as a marble. In simple terms marble was once a limestone which has gone through metamorphiss, transformation through high pressure and temperature which physically changed the stone.
The stone now has become marble although chemically the same as limestone, the stone has become hard enough and crystallised to be polished. As well as the process of heat and pressure natural disatsters like earthquakes also crack the stone then minerals in the earth fill these gaps(veining) then it is allowed to "bake"
Limestone primarily is sedimentary rock originating from different environments but with one thing in common in that they are made up of organic matter, calcite skeletons and marine organisims to name but a few. The main component of limestone is calcium carbonate more commonly known as calcite. Typical additional components can be clay, sand, silt and even flint can be found in some.
The texture of limestone varies from compact and even porcelain like to coarse and medium grain type. Colours vary from white to yellowish right through pinks and reds all the way to black in some instances.
Any rock or stone classified as granite should be of the igneous type. In real life this is quite often not the case. Most rocks that can be polished and do not resemble Marble, Travertine or Onyx seems to be labelled as Granite. A lot of these so called granites are igneous but their chemical structure is miles apart. We have true granite but then we have many other rocks that are traded as granite but are not. The most common of these are those of volcanic origination namely basalt. Legally it is fraud of course as many "granites" are of dubious origins and geological classification which in essence means they contain either binders made of calcite and or other acid sensitive materials. Care should be taken because this type of stone will in most cases not perform like a true granite. Careful consideration should therefore be exercised in the choice of stone and the ultimate expectations.