Under pressure and heat over years limestone forms to marble in the 3-5 miles below ground. These pressure and heat changes the limestone’s texture and shape.
This process called re-crystallization. Fossils in the limestone and carbonate minerals re-crystallize and form to calcite (caco3 –It is a type of very hard mineral. Mohs hardness of 3)
Impurities in the limestone during affect the mineral composition of the marble which is formed. At low temperatures, silica in the carbonate minerals form masses crystals of quartz. At higher temperatures, the silica reacts with the carbonates to produce diopside and forsterite. At a very high temperatures, rarer calcium minerals, such as larnite, monticellite, and rankinite, forms in the marble. If water is present, serpentine, talc, and certain other hydrous minerals may be produced. The presence of iron, alumina, and silica may result in the formation of hematite and magnetite.
The minerals come from impurities give marble a large variety of colors. The purest calcite marble is white in color. Marble containing hematite is reddish in color. Marble that has limonite is yellow, and marble with serpentine is green in color.
It is very difficult split marble equally, must be mined with care. Marble dug in block shape then those blocks are cut with saws to different shapes and sizes.
Marble does not split easily into sheets of equal size and must be mined with care. The rock may shatter if explosives are used. Blocks of marble are mined with channeling machines, which cut grooves and holes in the rock. Miners outline a block of marble with rows of grooves and holes. They then drive wedges into the openings and separate the block from the surrounding rock. The blocks are cut with saws to the desired tile shape and size.
Mohs Scale of Hardness
In 1812 the Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773-1839), who selected the ten minerals because they were common or readily available. The scale is not a linear scale, but somewhat arbitrary.
Hardness |
Mineral |
Associations and Uses |
1 |
Talc |
Talcum powder. |
2 |
Gypsum |
Gypsum is formed when seawater evaporates from the Earth’s surface. |
3 |
Calcite |
Limestone, marble and most shells contain calcite. |
4 |
Fluorite |
Fluorine in fluorite prevents tooth decay. |
5 |
Apatite |
When you are hungry you have a big "appetite". |
6 |
Orthoclase |
Orthoclase is a feldspar, and in German, "feld" means "field". |
7 |
Quartz |
|
8 |
Topaz |
The November birthstone. Emerald and aquamarine are varieties of beryl with a hardness of 8. |
9 |
Corundum |
Sapphire and ruby are varieties of corundum. Twice as hard as topaz. |
10 |
Diamond |
Used in jewelry and cutting tools. Four times as hard as corundum. |
Hardness of some other items:
2.5 |
Fingernail |
2.5–3 |
Gold, Silver |
3 |
Copper penny |
4-4.5 |
Platinum |
4-5 |
Iron |
5.5 |
Knife blade |
6-7 |
Glass |
6.5 |
Iron pyrite |
7+ |
Hardened steel file |
Our marble mosaic collections are made from the carefully cut and picked stone pieces.
