Granite is an extremely popular natural stone choice for countertops, and one of the many reasons that people love it is that it comes in so many different colors.
Have you ever stopped and wondered why it comes in so many colors or what about its composition makes that possible?
Granite—What Is It?
Granite is a type of igneous rock that has large bits of minerals that can be seen by the naked eye. The most common colors that you’ll find are pink, white, gray, and black.
How Is Granite’s Color Determined?
Granite is a natural stone that’s made up of other types of minerals like quartz, potassium feldspar, mica, amphiboles, and trace amounts of other materials. A typical slab of granite will contain 20–60 percent quartz, 10–65 percent feldspar, and 5–15 percent mica. The color of the granite depends on the amount of each of these minerals that it contains.
The proportions of these minerals have a lot to do with the molten rock that cooled to the original form of the granite. If that molten rock had a large quantity of potassium feldspar, it’s likely that the granite would take a pinkish color. If the molten rock had a large quantity of quartz and amphibole, the granite is more likely to be black and white speckled—which is a very common pattern seen on countertops.
Minerals and Colors
To follow is a list of minerals that can be found in molten rock and the primary color that granite will take if a high amount of this mineral is found.
- Quartz = milky white
- Feldspar = off-white
- Potassium feldspar = salmon pink
- Biotite = black or dark brown
- Muscovite = metallic gold or yellow
- Amphibole = black or dark green
Combinations of any of these minerals create the colors that granite is best known for.
Types of Granite and Their Color
Keep reading for a number of granite types, along with what it takes to create the color of said type.
White granite is made up mostly of quartz, which gives it a milky white appearance, and feldspar, which lends a hand in the off-white category. If there are black spots in this type of slab, that’s because of the presence of amphibole grains.
If you come across a rock that’s 100 percent white, with no grains to speak of, this is probably not granite—more than likely, it’s something man-made, like quartzite that’s made to mirror granite’s look.
“Granite” that is 100 percent black, much like “granite” that is 100 percent white, is not granite at all. For a material to qualify as granite, it must be 20 percent quartz, and it’s impossible for a material that is 20 percent quartz to be completely black.
Most likely, a completely black stone that claims to be granite is in fact something called gabbro, another type of igneous stone.
Pink granite is created due to a high concentration of potassium feldspar. Within this type, you should be able to spot small specks of milky, translucent quartz, dark speckles of amphibole, and white feldspar. Even though the primary mineral is potassium feldspar, in pieces of genuine granite, these should still be visible.
Black and White Granite
Black and white granite has an equal amount of quartz, feldspar, and amphibole, which creates a speckled look of black and white. This is a very common type of granite that you’ve probably seen used on countertops before.
Red granite is a variation of pink granite that’s rich in potassium feldspar—but the feldspar takes on a redder color rather than a pink one. You can also get a red hue from iron oxide that’s present in hematite grains included in the feldspar—the same process that gives rust its reddish color.
Unfortunately, if you see something that’s advertised as blue granite, it’s most likely not genuine granite. It’s probably something called larvikite, which is another type of igneous rock and sometimes referred to as “blue granite”—even though it’s not granite. Another type of rock that it could be is anorthosite, which contains a large amount of blue labradorite and is oftentimes marketed as “blue granite.”
Much like “blue granite,” “green granite” is once again most likely not granite. It’s probably a variation of marble that contains serpentine or a green version of soapstone that’s being sold as granite.
Many rocks contain minerals that give them a green hue, but granite is typically not one of those rocks. Green granite is possible through amazonite, a green variety of feldspar, but this is very rare.
Your Colorful Stone
At Sanford Granite, we pride ourselves in being the experts in all things countertop—especially when it comes to granite. We hope by reading this article that you understand a bit more about granite than you did going in and that you can use this information to guide you with future countertop choices.