Granite is a common rock that is often used in building materials and is made of quartz, feldspar and mica. Find out how granite can produce crystals with information from a science teacher in this free video on physical science lessons.
Hi, I'm Steve Jones, and I'm going to tell you some facts about granite. Now, granite is a very common rock, and it's probably one of the most nice rocks, to use for building materials, and if you look at banks, very often they're covered in granite, and it's interesting, that you get very different colors. The reason for that, is because of the way it is made up. What is granite? Well, the answer is, it is a rock made up of three basic minerals, or three or four basic minerals. Quartz is one of the main two. That's grayish material, when you look at it, but normally, it's actually transparent. Feldspar is of two types, which is alkaline feldspar and non-alkaline. The alkaline can be white, or pink, or blue, so the feldspars tend to be different colors, and that's what gives granite its color. If it's white granite, it's basically overall, white in color, with specks of black. If it's pick granite, you've got large crystals, pink crystals, with black and gray in as well, and the blue granite, which is quite unusual, is really bright blue, but contains also the gray and the black of the quartz, and the mica. The mica, although we say it's brown or black, when it's in the granite, it looks very dark, almost black. The crystal sizes of the granite, are between 2-5 mm, quite big, easily big enough to see, so if you look at granite, you can see the separate crystals, so if you go to the bank, and you see that lovely polished granite, you will see the actual crystals of the granite. You'll see very often they're pink, actually, pink, gray, and brown, or black. Sometimes there's pink and white, two types of feldspar in the granite, as well. This composition, we get two other types of rock, basalt, and gabbro. Now, the difference is, the granite cooled very slowly, so it's very slow cooling, which produces big crystals. The basalt however, cooled very, very quickly. That's because it was forced in between cold layers of rock, and cooled almost immediately, to solid, so it produces very small crystals. Gabbro cooled just slowly, so it cooled quicker than granite, but slower than basalt, and therefore, its crystals were smaller than those of granite, so when you go next time to the bank, and have a look at the outside, have a look at that beautiful polished stone. Look for your crystals. Look for the pink crystals very often, or blue or white, but look for those crystals and the gray, and the black, and you'll know it's granite.