Marble And Granite Industry

Marble and granite industry is considered one of the oldest and largest industries in the world. Marble and granite have been used in Egypt since the time of the ancient Egyptians. Historically, the industry moved from labor-intensive to capital-intensive with the advent of technological advancement, including development of automated production tools such as cranes and diamond-cutting wires. Marble consists mainly of calcite or dolomite, or a combination of these carbonate minerals. Marble is a type of metamorphic rock formed from limestone. It is formed from limestone by heat and pressure in the earth's crust that causes the limestone to change in texture and makeup (recrystallization process). Impurities present in the limestone during recrystallization affect the mineral composition of the marble that forms. The minerals that result from impurities give marble wide variety of colors. The purest calcite marble is white. Marble containing hematite has a reddish color. Marble that has limonite is yellow, and marble with serpentine is green.28 The specific gravity of marble usually ranges from 2.5 to 3, while granite has a very high specific gravity and can go up to 9.

Marble consists of soluble residue (0.89 percent), Fe2O3 (0.28 percent), CaCO3 (97.74 percent), MgCO3 (1.22 percent), phosphoric acid -(0.04 percent), along with the impurities: SiO2, Fe2O3, limonite, manganese, Al2O3, and FeS2 (pyrite).29 Granite, the hard natural igneous rock having visible crystalline texture, is formed essentially of quartz and orthoclase or microcline. It is formed from volcanic lava. The principal constituents of granite are feldspar, quartz, and biotite. However, the percentage composition of each varies and accordingly imparts different color and texture to the final product. The percentage composition of feldspar varies between 65 and 90 percent, of quartz can extend from 10 to 60 percent and that of biotite lies between 10 and 15 percent.30 Granite consists of silica (SiO2), 70 to 77 percent; alumina (Al2O3), 11 to 14 percent; potassium oxide (P2O5), 3 to 5 percent; soda (Na2O), 3 to 5

percent; lime, 1 percent; iron (Fe2O3), 1 to 2 percent; iron (FeO), 1 to 3 percent; magnesia (MgO), 0.5 to 1 percent; titina, less than 1 percent (.38 percent); and water (H2O), 0.03 percent.30

Nature has gifted Egypt with large deposits of high-quality marble and granite. Since 2700 b.c., the Ancient Egyptians used granite to build their important temples and buildings. Ancient Romans, as early as the third century b.c., acquired the Egyptian knowledge in quarrying and cutting the ornamental stones, especially granite. This technology was transferred back to Italy and, due to the natural endowment of Italy coupled with the acquired technical knowledge, the marble industry flourished and the Italians became world leaders in the production of marble. The production of marble passes through several stages.31 The main stages are demonstrated in Figure 1.26:

1. Exploration and identification of a quarry location. The locations are identified, followed by testing and verification of characteristics of the marble quarry.

2. Extraction of marble from the quarries. Extraction of the marble stone happens in several ways, depending on the technology owned by the quar-rymen. Marble does not split easily into sheets of equal size and must be mined carefully.

Marble Mining Wayswww.aucegypt.edu/academic/eco-nomics/papers/wk6.pdf, Accessed July 5, 2007.)"/>
FIGURE 1.26 Marble production process (Source: Azza Kandil and Tarek Selim, "Characteristics of the Marble Industry in Egypt," www.aucegypt.edu/academic/eco-nomics/papers/wk6.pdf, Accessed July 5, 2007.)

3. Lifting and transportation. After cutting the rocks of marble, marble blocks need to be lifted to a truck for transportation to the factories.

4. Inventory management. The inventory of raw stone blocks is very bulky and requires a very spacious area.

5. Cutting the stone into slabs and tiles. When a certain order is placed, the raw stone block is transported to the factory to be cut as demanded, either into tiles or slabs of various thicknesses (usually 2 cm or 4 cm). Stone cutting is a lengthy process that can take more than a continuous 12 to 16 hours of operation, depending on the model of the cutting machine, as well as the status of its diamond wire or diamond blades.

6. Polishing. After the stone has been cut to the specific dimensions, there are different techniques towards reaching a "finished" product. The most known of these techniques is polishing. The polishing operation is fully automated, with the use of powdered abrasives that keeps on scrubbing the surface of the marble until it becomes smooth and shiny. The smoother the abrasive used, the shinier and smoother is the surface of the marble. Here, water showers are essential to prevent overheating.

7. Distribution to end users. The distribution channels depend very much on the end product produced by the factory. If the factory produces finished tiles and slabs, then this is a finished order, processed according to the customer requirements, and a customer delivery takes place. Distribution often goes to workshops that are usually the middleman between the supplier and the end user. These workshops receive the cut plates of marble and store them in their shops for the end user to choose from.

Marble and Granite Waste

Nearly 70 percent of this precious mineral resource gets wasted due to mining, processing, and polishing, as shown in Table 1.6. The processing waste being dumped on the riverbeds is threatening the porosity of aquifer zones.32 However, for each marble or granite slab of 20 mm produced, a minimum of 5 mm is crushed into powder during the cutting process. This powder flows along with the water, forming marble slurry. In other words, a minimum of 20 percent marble/granite produced results in powder in the form of slurry. This slurry has approximately 35 to 40 percent water content. In India, about 30 percent weight

TABLE 1.6 Waste Distribution among Different Phases

Process

Marble

Mine

Processing

Polishing

Total

Mine Out

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Responses

  • annie
    How is marble extracted before technological development?
    1 year ago
  • george
    What is the use of marble for engineering purpose?
    10 months ago
  • HOBSON
    Are mining engineers involved with kitchen granite?
    8 months ago

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