What is granite? Granite types, facts, forms and usage. Inf about granite stone, rock
Granite is one of the rocks that were formed by the slow coolling of hot molten (liquid) rock. It is made up mainly of crystals of quartz and feldspar, and sometimes mica and hornblende.
Granite was usually formed deep in the earth. Thus, if it is seen on the surface it is because the rocks lying on top of it have been worn away by wind, water or ice, or because it has been pushed upwards by movements of the rocks long ago. It often forms the heart of mountain ranges, as in the Grampians of Scotland, the Coast Range of British Columbia (Canada) and the Australian Alps. Metals such as gold, silver,
c0pper, tin, zinc and lead are found in areas of granite, often in the surrounding rocks.
Granite is one of the hardest of all building stones. It is therefore difficult to handle, and before people had modern tools and machinery to cut stone and make it suitable for building, granite was used only for large buildings that made the work worthwhile or for rough buildings where rough stone could be used. Now that more efficient tools and machinery are available, granite is used even for slender pillars and other fine work. It is usually pinkish grey in colour, but is also found in mahogany red, white and shades of grey and pink.
The ancient Egyptians used granite for their statues and for parts of their great tombs, palaces, temples and pyramids. Many of these are still standing after thousands of years. The city of Aberdeen, in Scotland, is built largely of a pink granite obtained near by, and is often called the “Granite City”. Granite from Cornwall is lighter in colour, and was used to build the Embankment along the River Thames in London.
Granite can be quarried, or taken from the earth, in two ways. Sometimes holes are drilled in the rock a few inches apart, and steel wedges are driven into these holes to break off a block of granite from the whole mass of rock in the mountainside. This is called the “plug and feather” method. The more usual method, however, is to use high explosives. Holes are drilled into the rock and filled with explosives which, when set off, break great blocks of rock away from the main mass. The blocks are then broken into smaller pieces by the plug and feather method.
If large blocks of stone are wanted for building, gunpowder is used for the blasting, as it causes a fairly mild explosion. If the stone is to be used in smaller pieces as a foundation for roads, then more violent dynamite is packed into the holes. After they have been broken off, blocks intended for building stone are hauled on trucks to the dressing station where they are cut into the required shapes and sizes. Blocks intended for road building are taken to the crushing plant where they are broken down in massive machines to make “crushed rock”.