Welcome to Kuala Lumpur Sentral Station. The bustling centre of public transportation in Kuala Lumpur!
While not clearly apparent - there is more than meets the eye here.
What you find here is granite. Granite tiles. In their many shapes, sizes and of course...COLOUR!
But is the granite really granite? When is granite not granite? Not everything they say is granite is really granite.
Commercial granite tiles are often marketed as granite - black, blue, green, red, pink, white. But to truly qualify as granite - a specimen MUST contain at least 20% quartz to qualify as granite.
Granite is a conglomerate of minerals and rocks, primarily quartz, potassium feldspar, mica, amphiboles, and trace other minerals. Granite typically contains 20-60% quartz, 10-65% feldspar, and 5-15% micas (biotite or muscovite). The minerals that make up granite give it the unique colours we see in different types of granite.
The relative proportion of different coloured minerals in a granite is largely due to the original source of molten rock that cooled to form the granite. If the molten rock was abundant in potassium feldspar, the granite is more likely to take on a salmon pink colour. On the other hand, if the molten rock is abundant in quartz and minerals that make up amphibole, you will likely get a black and white speckled granite commonly seen on countertops.
The colours of granite
- Quartz – typically milky white colour
- Feldspar – typically off-white colour
- Potassium Feldspar – typically salmon pink colour
- Biotite – typically black or dark brown colour
- Muscovite – typically metallic gold or yellow colour
- Amphibole – typically black or dark green colour
The combination of the minerals above make up most of the colours we typically see in a granite. Now, let’s break down the distance types of granite and a quick overview of what gives them their colour
The colours of granite
White Granite
White granite is a granite that is composed primarily of quartz (milky white) and feldspar (opaque white) minerals. The small black specks in the granite above are likely small amphibole grains. This could be due to a lack of chemical components needed to form amphibole, or the cooling process was not amenable to formation of amphiboles.
If you see a rock that is 100% white, it is not granite but more likely a man-made rock that is created to look like granite or a quartz (quartzite) countertop.
Black Granite
“Black granite” is commonly seen in commercial rock, but it is not granite at all. As said above, granite must be at least 20% quartz, which means an all black rock is not a granite. Most commonly, black granite is in fact gabbro, a mafic intrusive igneous rock similar to basalt. Gabbro is primarily composed of minerals pyroxene, plagioclase, and small amounts of olivine (dark green) and amphibole.
Pink Granite
Pink coloured granite is a result of an abundance of potassium feldspar within the granite. You can see small specs of milky semi-transparent quartz, dark brown/black amphibole, and opaque white feldspar. However, in a granite like the one above the primary mineral is potassium feldspar.
Black & White Granite
The above granite appears to have equal parts quartz, feldspar, and amphibole, making a speckled black and white granite. This is one of the most common types of granite and one that is most commonly seen used for granite countertops.
Red Granite
Red granite is a variation of pink potassium feldspar abundant granite, where the k-feldspar takes on a redder than pinker colour. Also, you can get red colouring from iron oxide in hematite grains or inclusion within feldspar, essentially the same process that makes rusted metal ruby red coloured.
Bue Granite
You may find advertisements for blue granite countertops but this is also almost certainly not granite. One potential is that the rock is actually Larvikite, an igneous variety of monzonite and sometimes referred to as “blue granite” despite it not being granite. Another common alternative is Anorthosite, a rock that contains abundant blue labradorite and is sometimes sold as blue granite.
Green Granite
When advertised as green granite, often times the stone is actually a green variety of marble, which gains its green coloration due to inclusions of serpentine. It could also be a green variation of soapstone, mislabeled as granite. Granites are not abundant in green coloured minerals, but there are a variety of different rock types that do contain green minerals in abundance. One very unusual way to get a green coloration is the inclusion of amazonite, a green variety of feldspar.
How to claim this cache
1. How many colours of "granite" do you see on the floor of KL Sentral?
2. Which of these is not actually granite? Explain.
3. For each of the colours of granite identified here - explain why they possess that colour.
4. Take a picture of yourself or an identifier at KL Sentral Station with the colours of the granite in the background