Granite is some of the most distinctive rocks, and even amateur geologists can usually easily identify them. However, if you are new to rock geology, identifying any rock can be a daunting task. Don't worry, we have already provided you with protection. This is what you need to know.

Granite is igneous rock, sometimes called plutonic rock. This means that they were not formed by volcanic eruptions, but by the slow and gradual cooling of magma. They tend to have fairly large, coarse crystals (visible to the naked eye)—according to experience, the larger the crystal, the slower the cooling. For example, in other erupting rocks with extremely fast cooling rates, you cannot see the crystals with the naked eye, or there are no crystals at all-because they are too late to form. But for the granite named after the granular structure, you don't have this problem-you just see the crystals relatively easily. No equipment is required, although sometimes a magnifying glass can help.

Since granite is a very diverse group, their chemical composition may also vary. Most importantly, they contain silica, which accounts for 70% of its composition. They also contain aluminum oxide (approximately 14%), as well as small amounts of sodium oxide, potassium oxide, and iron oxide. Other compounds usually account for less than 1%.

Granite usually contains both "felsic" and "mafic" minerals. If you are only interested in identifying simple rocks, these names may not make much sense, but it helps to remember them in your geological exploration, especially when you want to identify more rocks.

Basically, felsic minerals are white (ish) white basic minerals are black. One tool I used when I was a student was that "mafia" sounds a lot like "mafia", which is terrible, so it's black. Felsic sounds a bit "fair" (I know it's not, but anyway-it helps), so they are whiter.

Generally speaking, granite is a felsic rock. In nature, basic minerals are secondary or accessory minerals. The two main minerals in granite are quartz and feldspar-in extreme cases, granite may only contain these two minerals, although this has almost never happened.

Therefore, the first two (quartz and feldspar) are felsic, they are white, while the others (usually hornblende, pyroxene, biotite) are black or very dark. You can also have accessory minerals such as tourmaline, beryl, topaz, zircon and apatite, but this will not help your identification. Let's take a look at the minerals that can help you:

Quartz is a very common mineral in the earth's crust and is almost always well represented in granite. According to the generally accepted definition, granite must contain at least 20% quartz.

Quartz is usually light gray, a bit like an opaque window. If you look closely at the crystals, they should stand out from the surrounding rocks. Quartz is very strong and you cannot scratch it with your nails (unlike other minerals).

Feldspar is usually the most abundant rock in granite-this is why the rock looks white with black spots instead of black with white spots. There are two main types of feldspar: alkaline feldspar and plagioclase. Most feldspar is a mixture of the two. It doesn't really help you distinguish between the two (unless you want to understand the mineralogy of granite in depth), and in most cases, you can't. However, identifying feldspar is the key to identifying granite.

Feldspar is almost everywhere in geology, from igneous rocks to sedimentary rocks. It makes up about 40% of the earth's crust, and knowing how to identify it is crucial for any geologist-hobbyist or professional. Feldspar is a hard mineral, almost always white (sometimes with a pink tint), and usually has a glassy luster. For example, the big difference between feldspar and quartz is the way it is broken. Although quartz breaks irregularly, usually in a curved shape, it is easy to break along a plane. This characteristic is called cleavage. Therefore, feldspar tends to look very massive, and its individual crystals may stand out compared to other minerals.

We treat these two as a whole because they have many similarities. They are all black, and if you look closely, they look like rising prisms. The main visual difference is that amphibole is usually higher than pyroxene, although this distinction is very difficult for non-professionals.

Chemically speaking, amphibole contains water, while pyroxene does not contain water, but again, this has nothing to do with basic identification. Look for a black prism that is a bit tall, unlike...

It is often difficult for amateur geologists to distinguish biotite from other black minerals, but there are a few things that can help you. First, biotite is basically a series of flat flakes, unlike hornblende and pyroxene, which are prisms. So black clouds are flat, and everything else is high. Due to its flaky structure, it often begins to split at the end, like an old book (hard to see with the naked eye). Biotite is also easily scratched by nails, which is a good judgment. Granite can also contain white mica (called muscovite), although this is much less than biotite

So black clouds are flat, and everything else is high. Due to its flaky structure, it often begins to split at the end, like an old book (hard to see with the naked eye). Biotite is also easily scratched by nails, which is a good judgment. Granite can also contain white mica (called muscovite), although this is much less than biotite

In general, it is not any of these minerals that make granite granite, but the way they are combined. The main gain is to see:

– Structure and texture. After all, granite is named after its "granular" or crystalline texture-as you can see-mineral type: look for quartz (at least 20%) and feldspar, usually containing mafic minerals

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Granite is one of the most easily recognizable rocks. It is entirely a matter of training your eyes and mind and should not take too long. In addition, if you are just starting out, you may read in some places that many rocks look like granite but are not real granite-they are called granite. Now, you shouldn't really worry about this and adopt the "If it looks like granite, then it is granite" method.

So, now that you know how to identify them...

Granite is widely distributed in the continental crust. You can't find them "everywhere", but you can find them almost anywhere. Without a global distribution or map of granite, the best way is to Google "Granite near [Location]" or contact your local geological museum or national survey organization (such as the U.S. Geological Survey or the British Geological Survey). Nevertheless, there are some general tips that may help.

Granite is usually relatively small, less than 100 square kilometers. They are usually associated with mountains, and remember that they have nothing to do with volcanic eruptions. Granite can vary greatly in crystal size and weathering, so don't expect them to all look like stock photos.

The most important thing is to explore and take notes by yourself, and then compare with the literature. Send us your photos and notes, we will surely select them for you!

Andrei's background is in geophysics, and he has been fascinated by it since he was a child. Feeling that there is a gap between scientists and ordinary audiences, he founded ZME Science-the result is what you see today.

© 2007-2019 ZME Science-Not exactly rocket science. all rights reserved.

© 2007-2019 ZME Science-Not exactly rocket science. all rights reserved.