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We take many things in the material world for granted, not realising or appreciating their presence or value. Construction materials that make up the material world around us come into this unconscious, “invisible” category. Though you see buildings, roads, footpaths and bridges every day, its almost certain that you have never thought about what the materials are, what they are made of, or where they come from. The vast bulk of our built environment is formed from raw materials won from the earth by the extractive industries. Without the raw materials with which to build houses, hospitals, schools, factories, roads, etc., life would certainly be more basic and less comfortable than we presently experience.

Stone quarrying is the multistage process by which rock is extracted from the ground and crushed to produce aggregate, which is then screened into the sizes required for immediate use, or for further processing, such as coating with bitumen to make bituminous macadam (bitmac) or asphalt.

The process begins with a detailed three-dimensional survey of the quarry face. This allows the explosives engineer to design the blast and to plot where the shot holes should be drilled so that the blast can be carried out safely and efficiently. The survey will show if there are any bulges or hollows in the face. A bulge will need more explosive than normal to ensure that it is completely fragmented and not left in place in the face. Hollow areas require less explosive than normal. The placement of explosives is professionally planned to ensure that the required fragmentation of the rock is achieved with the minimum environmental impact.

After the face profiling survey, the drilling contractor arrives. Using an air operated drilling rig, he drills the number of shot holes required, at the marked spots corresponding to the hole positions on the blast design, at the angles and depths required. After the shot holes have been drilled, they are surveyed to check that they correspond to the blast design and the two surveys are combined to allow the blast engineer to work out how each shot hole is filled with explosives.

Four giant in-pit crushers are taking shape at Citic Pacific mining ‘s Sino Iron project at Cape Preston in north west WA. They may be becoming manufactured by ThyssenKrupp, with components getting fabricated in Australia, Germany and China.

In terms of installation progress, a spokesman from owner Citic Pacific Mining (CPM) told the AJM in mid- February that “the first two of 4 crusher pocket slots are completed as well as the first in-pit crusher is becoming installed. The bucket wheel reclaimer installation is pretty much completed.

“In terms of start off up date, the initial shipment of ore is anticipated towards the latter component of this year.”

The in-pit crushers supplied will probably be gyratory, 60″ x 89″, using a capacity of 5,100 tph. They’ll be powered electrically by the project’s combined-cycle gas-fired power station and have been integrated into the mine style.

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