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An introduction to geology
An introduction to geology

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1.1 What is a rock?

What is a rock? This might seem like a simple question – rocks are hard things that are found in the ground and that mountains are made of – but unsurprisingly, it is more complicated than that. Basalt isn’t just made up of stuff called basalt and, believe it or not, there are lots of different things that can make up a sandstone. The following video explores this in more detail.

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Video 1.2 Three types of rock
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So, there are three different types of rock: igneous, sedimentary and metamorphic. These three types are formed in different ways. This means that they have different properties that, to the trained eye, usually make them easy to tell apart. But, what is a rock? A rock is an aggregate, or combination, of minerals. These can be all the same mineral, as seen in limestone, or more often, lots of different minerals, as seen in granite. So what is a mineral? Well, a mineral is defined as any naturally occurring element or compound which has a characteristic chemical composition, physical properties and, importantly, crystal form.