Quick and easy geology lesson highlights granite’s various shades. Granite is one of the finest countertop surfaces available. Have you ever wondered why granite comes in different colours and what that means? Let’s shine a spotlight on granite’s glorious grains to learn how this premium stone surface came to be.
Granite is a type of igneous rock. That means that it was derived, or solidified, from molten (melted) rock. Igneous rock is distinguished from sedimentary rock. That type of rock is made up of very visible layers, which settled over a long period of time.
Specifically, granite is made from molten igneous rock that cooled within a crust. As it cooled, crystals formed from the minerals within it. The size of these crystals – known as grains – is proportional to the speed at which the rock cooled. As well, since the rock cooled without having been expelled from a crust, the resulting grain make-up is not homogeneous. That’s what gives granite its many hues.
The different colours of granite are due to its mineral and rock make-up. In order to be considered granite, the rock must contain at least 20 per cent quartz, which is typically white in colour. Other minerals found in granite are feldspar, potassium feldspar and amphibole. These minerals add colours to it, too.
The Granite Countertop experts at StoneSense, Ottawa’s premier supplier of natural stone countertops, would be happy to explain granite’s derivation to you. But let’s talk about its specific colours first.
If the granite formed with a lot of amphibole and quartz it will tend to be a black and white speckled colour. If it formed with a lot of potassium feldspar it will likely be a salmon pink one. Granite formed of mostly quartz alone will typically be a milky white colour. A lot of amphibole, on the other hand, will result in a black or dark green colour.
White granite is composed primarily of quartz, responsible for the milky white colour, and feldspar, responsible for the opaque white one. If the granite contains small black speckles these are likely due to small amphibole grains.
Pink granite is formed from an abundance of potassium feldspar. Should it contain speckles of a milky colour these would be due to quartz. Black speckles would be from amphibole and opaque ones from feldspar.
Black and white granite would likely have equal parts amphibole, quartz and feldspar.
Red granite is similar to pink but with the potassium feldspar having more of a reddish colour. The red shade may also derive from iron oxide in the rock.
Granite has been used for thousands of years in construction and art. It is considered a status symbol. In addition to countertops, granite is used for floor tiles, building veneers and paving stone. It is the best-known and most common igneous rock found on Earth.
In the commercial stone industry, granite is defined, simply, as a rock with visible grains that is harder than marble. As a result, rocks other than granite itself may be referred to as granite. These include gabbro, basalt, and pegmatite.
A granite referred to as black would be composed of gabbro, for example, as actual granite must be composed of at least 20 per cent quartz and would have at least some white colour in it. A granite referred to as blue would also not actually be granite but likely another rock.
Notwithstanding, granite and other igneous rocks make countertops which are heat-resistant, scratch-resistant, and stain-resistant. As a premium countertop surface, granite – in all its colour splendour – is highly valued.
The Countertop experts at StoneSense have a large selection of granite in their showroom. They would be happy to explain it, and all its colours, to you. Drop by today!
