Marble
Marble is created by the limestone or dolomite metamorphosis. These rocks often have coarse crystals, which are different from sedimentary carbonate rocks. The main mineral that makes up most marbles is calcite, and they have minerals such as quartz, graphite, hematite, limonite, pyrite, etc. Other characteristics of these stones are listed in Tables 1 and 2.
Table number 1
| Property | Amount |
| Hardship | Marbles are more resistant if they contain some quartz or other silicate minerals |
| Special Weight | Average 2.7 tons per cubic meter |
| Water absorption | It usually has a water absorption of less than 1%. |
| resistance | It has moderate resistance and its deformation is elastic, plastic. Their compressive strength is between 19 and 140 MPa, and its average compressive strength is about 110 MPa. Its bending strength is between 15 and 6 MPa and tensile strength is 4 MPa on average. |
| porosity | Relatively low and between 0.3 and 1.2 percent |
| Color | As a group, marbles show a wide different colors range. Completely pure marble has a white and shiny color. The light gray to black color is caused by carbonaceous materials. Green colors are usually produced by chlorite or epidote, gauconite or other minerals. The pink and red color is due to the hematite or manganese carbonate very fine scattered particles presence, and the yellow and cream color is due to the limonite presence. |
Table number 2
| Property | amount |
| Water absorption coefficient | Maximum 0.2 percent |
| Special Weight | 2.305 to 2.8 grams per square centimeter |
| pushing resistance | At least 52 MPa |
| Tensile strength | At least 7 megapascals |
| Bending strength | At least 7 megapascals |
| Abrasion strength (friction) (Ha) | 10 |
Iran’s marble has a higher priority than other export marbles in terms of vast resources, colors variety and ingredients. Some of these stones, such as Karam Dedihi stone, are unique in the world in terms of hardness, processing capacity, diversity, beauty and color, and for this reason, they are considered luxury and expensive stones all over the world.
In Iran, the word marble is mistakenly used for the word marble. In fact, marble is a transformational stone. The stone that is known as marble in trade in Iran is equivalent to the word onyx marble and is a semi-transparent layered stone made of calcite. In fact, onyx has a higher transformation degree than marble.
Marble is divided into the following three categories according to the transformation and the composition mother rock intensity
- Chinese
- Crystal
- Cloudy
Marble types according to the transformation and the composition mother rock intensity.
Chinese stone:
Marbles are said to have a fully crystalline texture, the same size, full shape and fine grain, which are mainly calcite and a small wollastonite amount as the main minerals that make up it.
This name has been termed in Iran in the last two decades and apparently it was called Chinese because it gives a Chinese sound when struck in small thicknesses (about 2 cm).
Chinese stones have low color variation and are usually white or halo or yellow streaks. These stones are often divided into three categories according to color:
- White porcelain
- Chinese cloud
- black china
Of course, the colors variety is more than these and usually all three types can be seen in one piece of stone. Porcelain stone is formed in areas with low metamorphic intensity. There is little crystal direction in them, and the rocks that contain them are micaschists. Chinese stones are strong and healthy stones and can be used in almost all places of a building, even places that have a lot of water, especially health care centers, and it is also found in the form of axes.
crystal:
Coarse-grained marbles (visible to the naked eye), all crystalline, of the same size and shape are called crystals. Crystals are formed in areas with moderate to high transformation intensity (Akbarpour, 1367).
The crystal stones color is mostly dark to light gray. In the past years, the porcelain stone use amount in building construction, especially in the facade, was very wide, but due to this stone inefficiency in the facade and lack of suitable color variety, it was replaced by travertine and other similar products, for this reason, its production in the past years, to The intensity has decreased.
Cloudy:
Marmarite is said to contain light and dark minerals concentration non-parallel bands. This rock type is more abundant in areas with medium metamorphism intensity and it seems that it is formed in medium to high temperature metamorphisms (Akbarpour, 1367).
Sources
- Atai, (2017), Building Stones, Shahrood Technology University, 304 pages
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