CLASS SET – DO NOT WRITE ON
Rock VS Mineral
Can you tell the difference between a rock and a mineral? What makes a mineral so much different from a
rock? Explore these questions in depth, and learn how we classify rocks and minerals.
Rock or Mineral?
They say that a diamond is a girl's best friend. Rubies, sapphires and other precious gemstones are also
popular ways to impress a lady. Mankind has always been infatuated with rare crystals. Diamonds, in
particular, have become a symbol of love and commitment. Young ladies can't wait to show off when they
get a big shiny rock from the groom-to-be. But, should we really be using the word 'rock' to describe a
diamond?
You may have heard the phrase 'rocks and minerals' at some point in your science schooling. The reason
we say 'rocks and minerals' is because they are two different things. Rocks are not minerals, and minerals
are not rocks.
As we'll soon discover, diamonds are actually minerals. Some people are under the false impression that
minerals are things we eat, as in the phrase 'essential vitamins and minerals.' But really, minerals
encompass a broad range of natural substances, some of which you eat, some of which you forge into tools
and some of which you give to your future spouse. Let's talk about the differences between rocks and
minerals so we can get all our facts straight. We'll start right now with minerals.
Minerals
A mineral is a solid, inorganic, naturally-formed substance that has a crystalline structure and specific
chemical composition. I know that's a lot to take in, so let's break down this definition piece by piece.
First of all, minerals are solid and formed naturally in the earth. Natural solids can be familiar things like
sand, granite, salt and wood. Our definition says that minerals are inorganic, which means that they do not
consist of tissues from living things. So, that means that wood is not a mineral.
It also says that minerals have a crystalline structure. That means that the component atoms of the
substance have a repeating, 3-dimensional
arrangement. This is a picture showing how the
atoms of salt are arranged. Salt is also called
sodium chloride because it is made of two types of
atoms: sodium and chlorine. The sodium and
chlorine atoms are put together in a very specific,
3-dimensional lattice that repeats over and over
until you get to the end of the salt crystal. Yes, it's a
crystal! I know you typically don't think of salt as being a crystal. But it is, and so is sand. Sand is just tiny
chunks of quartz crystal, made by a pattern of silicon and oxygen atoms.
Minerals are also rare compared to rocks, which are found everywhere, and are generally considered a pure
substance. Meaning they are made of just one element or compound. You will also not find fossils in
minerals.
What about our last substance, granite? It's solid. It's formed naturally in the earth. It's inorganic. But does
it have a specific chemical composition? Does it have a regular, repeating atomic arrangement? No, granite
may be made up of minerals, but it's not a mineral itself. It's a rock.
CLASS SET – DO NOT WRITE ON
Rocks
A rock is an inorganic, naturally-formed substance without a particular atomic structure (not crystalline) or
chemical composition. It can be found in solid (chunks or pieces), liquid (lava/magma) or what is known as
a plastic-solid (which is just a very flexible solid structure that can bend easily) form. And they are made
up of two or more minerals, which means they are not a pure substance. Examples of rocks include granite,
limestone, marble, pumice, obsidian, sandstone, shale and slate. Each of these rocks consists of several
different minerals, which are mixed up inside the rock through a variety of geologic processes. One of these
processes can even lead to fossil formation
Let's take granite, for example. Granite is mostly composed of three minerals: quartz, feldspar and mica.
Each of these minerals can be found alone in nature, but here, they are mixed up inside of the rock.
Sometimes you see large chunks of one of these minerals inside of the granite. But, when you take the
stone as a whole, you have to call it a rock.
Other rocks are much finer grained than granite, so it's not easy to spot the different minerals. Slate is a
rock that was made from clay, and clay is composed of tiny, tiny particles. Those particles can be minerals
like quartz, pyrite, apatite, muscovite, feldspar, kaolinite, biotite, tourmaline - the list goes on! But you can't
see these minerals inside of a slate rock. The slate looks all the same color and texture. Still, it's not a
mineral because it has no regular atomic structure or chemical composition. Rocks are made of minerals,
and minerals stand alone.
Assignment: Now, copy the chart below onto page ______ of your notebook. Some of the information
is already filled in for you. You need to use the article to fill-in any missing information to show how
they compare or contrast.
Minerals VS Rocks
Minerals
Rocks
Only found in a solid form.
Made up of two or more minerals. In other words
made of many elements and compounds.
Does not have a particular shape to it.
Does not have fossils.
Examples include gold, salt, quartz etc.