Granite has come to be defined by the qualities of ruggedness and hardness, terms that it justly deserves. Visually, it lacks the fine grain of marble, instead the oaty, coarse mosaic grains that are typical of granite give an insight into its ingredients and its structure; it is made of up of mica (the shiny bits), feldspar and quartz. Granite is an igneous rock, a family of rocks made through the solidification of molten magma or lava cooled slowly under great pressure.
Granite comes in many forms and these are characterized by colour variations. As a material, it is distinguishable by its hardness, durability and ability to weather well, even when compared with other stones, such as marble. For example, as a building material, it can be enhanced by polishing to emphasize its crystals, creating a glass-like surface that it will retain for many years, even in external applications. Its density is similar to marble and quartz, but compared to marble it is much harder – granite has a Shore Hardness of 85–100, whereas marble’s is 45–56. It also has a much harder abrasive hardness, although well below that of quartz, and this is one of the reasons that it is so popular in kitchen countertops.
Image: Plus One salt cellar by Norway Says for Muuto
•High wear and abrasion resistance
•High density and hardness
•Polishes to a glass-like finish
•Each piece is decoratively unique
•More durable than marble
Sources
Granite is mined in various countries; the main ones include the UK, parts of Scandinavia, South Africa and Brazil.
Cost
Due to the hardness of the material the production has high failure ratio, with only a small proportion being sold. This combined with the hardness of the material makes it expensive to manufacture and mine.
Sustainability issues
Granite is obviously a non-renewable resource, and strip mining can cause harm to the environment through chemical pollution to air, earth, and water. Measures are being taken to limit wastage during mining and manufacture, and an increasing number of companies now offer recycling options.
Production
Hand-cutting, sandblasting, CNC cutting, laser cutting and water jet cutting.
Typical applications
Flooring tiles, kitchen countertops, gravestones and, due to its flatness and resistance to damage, in engineering applications to obtain a plane of reference for measurement. It is also used for roadside bollards and other architectural elements.
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–High wear resistance –Polishes to a glassy finish –More durable than marble |
–Expensive to mine and manufacture –Production has a high failure ratio |