Hi, I'm David Schultz. Welcome to our Earth, its climate, history and processes. In this lecture, I want to talk about minerals and rocks. To start off with, what are the definitions of minerals and rocks? Let's look behind me here. A mineral is a natural occurring, solid, crystalline substance, usually inorganic, with a specific chemical composition. So, let's look at these components of this definition to get a better understanding of what a mineral is. Minerals naturally occurring, so something like glass or concrete would not be a mineral. Solid crystalline substance, we need to have a crystalline substance in order to be a mineral. So, something like Opal, which is simply amorphous silica without a crystalline structure would not be considered a mineral. Usually inorganic, of course, we can have some organic minerals. With a specific chemical composition. That is the key. A mineral needs to be a specific composition that we can write down. So, for instance, here I've got a mineral, very large mineral here. This is called halite, it's sodium chloride, or table salt. So, it has a specific chemical composition NaCl. Here is another mineral, this is a muscovite. Mica, it's very thin, very laminar. You can see the crystalline structure to it, in this case is sheets of this mineral. The next definition is a rock. A rock is a naturally occurring, solid aggregate of minerals or, in some cases, a nonmineral solid matter. So, let's look at the components of this definition. Again, naturally occurring. A solid aggregate of minerals. So, it could be a single mineral. The halite here is also a rock. It's a mineral, but it is large enough to comprise a rock as well. Or, in some cases, nonmineral solid matter. So nonmineral solid matter might be something like coal, which is essentially compressed carbon and other substances from decayed plant and animal material.
