Granite is sourced from many continents around the world and although they differ in quality and crystalline structure all granites have three essential minerals in common:
Feldspar (50% or greater)
Quartz (25 – 30%)
Mica (3 – 10%)
These minerals occur in varying proportions giving granite its own natural colour, texture and structural characteristics.
In addition, hornblende, magnite, hematite, pyrite, zircon, garnet, corundum and other minerals may be present in smaller amounts, adding to the unique colouration and texture of each granite deposit.
With a natural material like granite a certain amount of "movement" or grain in the stone must be expected. Many people find this blending of colours to be the most compelling reason for using granite. From the moh's hardness scale of 1-10 granite falls within the 6-7 ranges whereas a diamond is 10.
World Sources of Granite
The majority of the world continent have deposits of indigenous granite. However, in many cases due to young age of the continent or because of the substructure sound granite blocks cannot be sourced economically. The world's major granite producing countries are South Africa, North and South America, Sweden, Finland, Norway and India.
Australia also has huge tracts of granite which are used extensively throughout Australia whilst in New Zealand our commercially used granite is restricted to Coromandel granite. Bluff granite was used quite extensively during the 1940's and 1950's - this quarry is no longer viable.
Granite has been quarried systematically as far back as 4000 BC long before hardened metals were used. Over the centuries quarrying techniques changed very little, remaining relatively unsophisticated. Then in the late 1880's new quarrying technologies were introduced that made it possible to use granite as a cost effective building or monumental stone. Quarrying operations were then modernised by using compressed air to drive rock drills, outlining the block with closely spaced holes. Then wedges could be used to break loose blocks of specified sizes and shapes.
Quarrying techology continues to advance. One method of quarrying granite uses a gas flame to burn channels along the sides of a block. Then holes are drilled with gang drills along the back and bottom of the block. Soft explosives are used to separate the "quarried-to-order" granite piece. A front end loader can then lift the block from the quarry and load it on a truck bed for shipment to the fabrication plant.
A block of raw black granite being cut into slabs by a large diamond tipped saw.
Typical stone quarry face
Stone block being transported
Excessive weight for fork loader