Nonmetallic Minerals

The most important non-metallic minerals in the building industry are lime and silicon dioxide (Table 6.5).

Quartz is almost pure silicon dioxide and is the hardest of the ordinary minerals. It is the main constituent of glass and silicone, and is an important ingredient in Portland cement. Pure quartz is as clear as water and is known as rock crystal. Normal quartz is unclear and white or grey, and is found in granite, sandstone or quartzite, or the sand of these rock types.

Pure limestone is a monomineral rock type of the mineral calcite. Accessible sources of limestone appear as veins or formations in many different types of rocks of different ages. Limestone is used in a variety of products; it is one of the most important construction materials in the world after sand, gravel and crushed stone. The largest consumer of limestone is the cement industry. Cement nowadays means Portland cement, which is produced from a mixture of two-thirds ground limestone, clay, iron oxide and a little quartz, heated to 1500 °C. Gypsum is added to the mixture and then it is ground to a fine cement.

Limestone is an importantfiller in industries producing plastics, paint, varnish, rubber and paper. Some limestone is also used in the production of glass and fibreglass to make the materials stronger. In the metal industry, limestone is used to produce slag.

In addition to quartz and limestone, there are many non-metallic minerals of rather more limited use. Important are gypsum, used in plasterboard and certain cements, potassium chloride and sodium chloride, which form the base of a whole series of building chemicals, partly in the plastics industry, and kaolin, used as a filler in plastic

Table 6.5 Important non-metallic minerals in the building industry

Mineral

Areas of use

Anhydrite CaSO4

Plaster; mortars

Asbestos (group)

Thermal insulation; reinforcement in concretes, plasters, mortars, gypsum products and plastics

Borax Na2B4O7 x 10H2O

Biocides; flame retardants; production of glasswool

Boric acid B(OH)s

Biocides; flame retardants

Calcium silicates (group)

Glass; glazing on ceramics

Dolomite CaMg(CO^2

Filler in plastic and paint; production of magnesium; production of glass and fibreglass

Gypsum CaSO4 x 2H2O

Sheeting; plaster; Portland cement

Ilmenite FeTiO3

Pigment in paints (titanium white), filler in plastics

Kaolin Al2Si2O5(OH)4

Pozzolana cements, filler in plastics and paint

Limestone CaCO3

Mortars; plasters; pozzolana cements; Portland cement; lime sandstone;binder in cements; production of glass and fibreglass; paints and lyes; production of steel

Magnesium carbonate MgCO3

Cements

Mica (group)

Production of vermiculite, fireproof glass

Montmorillonite AUSi8O2o(OH)4 + H2O

Waterproofing

Olivin (Mg, Fe)2SiO4

Filler in plastics, aggregate in concretes

Potassium chloride KCl

Production of glass

Sodium chloride NaCl

Soda; waterglass; production of glass; production of chlorinated plastics

Silicon dioxide SiO2

Pozzolana cements; production of glass; production of mineral wool; production of silicone

- as fossil meal (diatomite)

Pozzolana; thermal insulation; filler in plastics and paints

- as perlite

Thermal insulation

Sulphur S

Concrete, plasters, production of flame retardants and fungicides

Talc Mg3Si4Oio(OH)2

Filler in plastics

materials and paints. Asbestos, which was widely used earlier this century, is now more or less completely out of use as a result of its proven health damaging properties.

Generally, the resources of non-metallic minerals are much greater than for metals. Similarly, the energy needed in their production as well as associated pollution is far less. Tables 6.7-6.9, on the other hand, show that use is very widespread; industries such as the glass industry release large amounts of greenhouse gases. One product stands out in particular: the cement industry alone accounts for no less than about 5% of the total global emissions of carbon dioxide (The Cement Sus-tainability Initiative, 2002).

Extraction of these minerals usually takes place in open quarries, where stones with the lowest impurity content are cut out as blocks, broken down and ground. In a few cases, the minerals can be found as uncompacted material. One important example is quartz sand.

jTable 6.6 Basic materials

Material

Main constituents

Û.

Hydraulic and non-hydraulic cements

Lime; Quartz; Gypsum; Sulphur; Magnesium oxide; Fossil meal; Ground bricks; Fly ash; Clay; Blast furnace slag; etc.

Structural concrete; concrete flooring, roofing and wall cladding; plasters; mortars; fillers; foamed up as a thermal insulation

Glass

Quartz; Lime; Dolomite; Calcium silicate;

Openings for daylight in doors and windows;

Soda; Potash

glasswool or foamglass as thermal insulation; external cladding

Sodium water glass

Soda; Silicon dioxide

Additive in cements; flame retardant and insecticide in timber and plant products; silicate paints; adhesives

Potassium water glass

Potash; Silicon dioxide

Silicate paints; adhesives

Extraction involves large quantities of material being moved, causing large scars on the landscape. As with the metallic ores, serious damage can be caused to local ecosystems and ground water that can be quite difficult to restore later. Certain minerals such as lime and magnesium can be extracted by electrolysis from the sea, where the direct environmental impact is somewhat less.

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