Quarry Southern Africa November 2018 - Page 23

WINNING ‘interesting’ couple of months. “As to the future I believe that we are in for a very tight three years or so, before we see an improvement in the construction industry.” He describes the primary challenge to the ready-mix concrete business as being one primarily of saturation of the market. “There are so many players competing for a pie which is shrinking, and as a result the price of ready mixed concrete is being driven down. Ready-mix concrete, as much as aggregate, is a highly cut-throat business which comes down to very tight margins, requiring operators to run a tight ship,” says Mandass. Strerkspruit’s ready-mix plant makes product to client specifications. The concrete industry has evolved a long way from where it used to be, and Mandass says it [concrete] “can do some weird and wonderful things today.” Coloured concrete is an example of such an evolution, he says, “The colourant added is very expensive, but the final product is beautiful for a commercial driveway for instance. This is very technical because if you lay a colour down it needs to be consistent.” Quartzite is mined and used to manufacture glass, ferrosilicon, manganese ferrosilicon, silicon metal, silicon carbide and other materials. What is quartzite? plate boundaries. There, sandstone is metamorphosed into quartzite while deeply buried. Compression at the plate boundary fold and fault the rocks and thicken the crust into a mountain range. Quartzite is an important rock type in folded mountain ranges throughout the world. When the mountain ranges are worn down by weathering and erosion, less- resistant and less-durable rocks are destroyed, but the quartzite remains. Wise geologists won’t hit quartzite hard with a rock hammer. If they do, they will make sure they are wearing impact-resistant goggles, gloves, long sleeves, long pants and sturdy shoes. A sharp hammer blow usually bounces off, sometimes causing injury. When the rock does break, the impact often yields sparks and sharp pieces of rock travelling at high velocity. Quartzite is a metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure and chemical activity of metamorphism. These conditions recrystallise the sand grains and the silica cement that binds them together. The result is a network of interlocking quartz grains of considerable strength. The interlocking crystalline structure of quartzite makes it a hard, tough, durable rock. It is so tough that it breaks through the quartz grains rather than breaking along the boundaries between them. Quartzite is usually white to grey in colour. Some rock units that are stained by iron can be pink, red or purple. Other impurities can cause quartzite to be yellow, orange, brown, green or blue. Its extreme toughness made it a favourite rock for use as an impact tool by early man. It could be shaped into large cutting tools such as axe heads and scrapers, though its coarse texture made it less suitable for producing tools with fine edges such as knife blades and projectile points. Most quartzite forms during mountain-building events at convergent www.quarryonline.co.za  Uses of quartzite Quartzite has a diversity of uses in construction, manufacturing, architecture and decorative arts. Although its properties are superior to many currently used materials, its consumption has always been low for various reasons. In architecture, marble and granite have been the favourite materials. Quartzite, with a Mohs hardness of seven along with greater toughness, is superior to both in many uses. It stands up better to abrasion in stair treads, floor tiles and countertops. It is more resistant to most chemicals and environmental conditions. It is available in a range of neutral colours that many people prefer. The use of quartzite in these uses is growing slowly as more people learn about it. Quartzite’s soundness and abrasion resistance are superior to most other materials. Unfortunately, the same durability that makes quartzite a superior construction material also limits its use. Its hardness and toughness cause heavy wear on crushers, screens, truck beds, cutting tools, loaders, tires, tracks, drill bits and other equipment. As a result, the use of quartzite is mainly limited to geographic areas where other aggregates are not available. Quartzite is valued as a raw material because of its high silica content. A few unusual deposits have a silica content of over 98%. These are mined and used to manufacture glass, ferrosilicon, manganese ferrosilicon, silicon metal, silicon carbide and other materials.  QUARRY SA | NOVEMBER/DECEMBER 2018_23