Science. Communication. Community.
If you want a high-fashion kitchen these days, granite countertops are a must. But what is granite, really — and how did this particular rock end up in our kitchens?
Last month, after experiencing an exhausting cross-country move, my husband and I were tasked with finding an apartment. In our dozens of tours, I began noticing a persistent kitchen and bathroom theme: granite.
I watch HGTV and I’ve walked through home improvement stores; the American hunger for granite countertops is not lost on me. (In fact, I even wrote about the rise of designer kitchens for The Salt at NPR last summer). But as a science-minded lass, I had to wonder: what exactly is granite made of, and why is this specific geological formation suddenly such a designer buzzword?
To address my quarry-related quandaries, I turned to geologist Brooke Norsted, assistant director at the University of Wisconsin Geology Museum. Below are a few excerpts from our conversation, edited for length and clarity.
I know granite is a type of rock, and I know people go crazy for it in kitchens. Can you tell me a little bit more?
Granite is an igneous rock, the word igneous meaning ‘from fire.’ So these are the kinds of rocks that form from volcanos. Deep underground in the magma chamber under the volcano, there is this mass of melted rock. The [melted rock] can come out the top of the volcano in an eruption – like we’re familiar with – and cool off and turn to rock outside. But in another option – when there is not an eruption – the magma chamber can cool off and solidify underground, and that’s what forms granite. When that magma slowly cools underground.
Molten rock cooling off under the Earth’s surface? Sounds like that could take a while.
It takes hundreds of thousands of years for these magma chambers to cool off. And then after that, we have to wait even longer. We find granite at the surface of the Earth, meaning that you had enough time for the magma chamber to cool off, and for the volcano itself to have eroded away, so that the cooled magma chamber is at the surface of the Earth and you can collect it and turn it into countertops.
Magma, then cooling, then erosion. Got it. But why is granite the stone of choice for kitchens?
Granite can be very beautiful. Granite in a countertop is polished, and you can see the edges of these different colored grains. They’re crystals of different minerals that have cooled together underground. Marble is also beautiful, but marble would be susceptible to acid, which etches away at it. The minerals that make up granite – like quartz – are very hard and resistant [to etching and scratching].
What are the types of minerals that are found in granite?
The word granite to a geologist means that the rock has a combination of a certain suite of minerals, which are feldspar, quartz, and mica. That said, a lot of what people have on their countertops is not granite. It’s become kind of an industry word for any kind of rock that people use to make countertops. If you think about all the volcanoes that have ever been on Earth, each one has it’s own specific chemistry and is a little bit different … it would be hard to pinpoint exactly what quarry each countertop came from to say if it was actually granite or not.
But why is granite – and apparently imposter granite – so expensive? Is it in short supply?
I haven’t heard of anything like that [a granite shortage], but the whole process of getting it out of the ground and polishing it is not insignificant. Especially if it’s being shipped from wherever and cut to size. Also, once you cut something to shape, if you want it polished, you have to go from very coarse to very fine polishing, and it takes a lot of time. I think it’s the person-hours that go into making the granite countertop that make it so expensive.
Finally, since you’re a geologist (and since red granite is the state rock of Wisconsin) do you have granite in your kitchen at home?
I do not. I have a faux-plasticy-granite countertop. I wish I got paid enough at the geology museum that I could have a real granite countertop. It seems like all geologists should just have them by default, right? [Laughs.]