What is the chemical composition of minerals? We’re gonna start off with a little bit of chemistry here.
Minerals have been composed of elements. Some of the elements that they’re mostly composed of are oxygen and silicon. We could take this oxygen and silicones, and combine them to create what is called a silicon-oxygen tetrahedron.
If we look at the composition of the earth’s crust because remember these minerals come from the earth’s crust. Rocks come from the earth’s crust. We can actually see the elements that make it up and notice we have oxygen and silicon.
We can notice that oxygen and silicon, two make up the most. The silicon-oxygen tetrahedron that I just mention a little bit earlier is something a little bit different. It’s the basic structural unit that facilitates minerals. But this is what we have four oxygen surrounding one silicon ion.
Oxygen and silicon make up the silicon-oxygen tetrahedron that is found within an animal atom inside a number of different minerals. Diamond has some of their arrangements of atoms that look somewhat similar but they’re a little bit different.
Notice that galena has a nice structure. The physical properties of a mineral are determined by the internal arrangement of atoms. So these repeating patterns that we see such as diamond, talc, or galena are gonna help make those minerals what they are.
Halite has got cleavage because of its internal arrangement of atoms. The graphite is nice and soft. It is used to make pencils. Lead inside pencils has an internal arrangement of atoms that are loosely packed. It’s soft which is great for pencils. Remember what determines the mineral.
It’s the hardness and cleavage. These atoms are set up in either repeating patterns or whatever patterns. It is going to determine how it breaks, how hard it is, and a number of different other properties.
Chemical composition of minerals
Elements
Elements are basic blocks of minerals. There are over a hundred known. ninety-two of those are naturally occurring.
Atoms
Next, we have atoms. It is the tiniest part of the matter. It retains all of the characteristics of an element.
Atomic structure
Next, we have an atomic structure. We have the nucleus, which contains the protons and neutrons.
Electrons
Then we have electrons that are going to surround the nucleus and these are negatively charged ions and then we have energy levels or shells that go out from there.
Bonding
All right let’s see about the different types of bonding. So this is pretty important. We’re gonna take chemistry. We just talked about and applied it to the different types of bonds that minerals can have. The next type of bonding we’ll talk about is covalent.
Atoms share electrons. Next, we have other bonds. We have both ionic and covalent bonds and may occur in the exact same compound but we’re also gonna get metallic bonding. Valence electrons are free to migrate. Metallic bonding is pretty typical of metallic minerals.
Isotopes
Alright, next we’re going to talk about isotopes and a little bit about radioactive decay. A mass number is going to be the sum of neutrons plus protons and in Adams nucleus, we have an isotope.
The variance of the same element with one or more mass numbers and then some isotopes have unstable nuclei and emit particles at energy and a process that’s called radioactive decay.
These are a few chemical compositions of minerals.
How are minerals formed?
Things precipitate out from a solution. We’ll first start with a fluid that is completely saturated with dissolved material that won’t precipitate minerals until there’s a temperature drop or there’s a water loss. Know more about mineral formation.
Once that starts happening and then the different minerals form. When they form from the molten rock when magma is really hot molecules are moving around but when it slowly starts to cool the atoms slow down and they combine. So this combination is called crystallization.
Physical properties of minerals
Now we’re going to get into the different physical properties of minerals and this is where we really start to talk about how you would identify them.
The first physical property we’re going to cover is crystal form. This is going to be the external expression of the orderly internal arrangement of the atoms, so that’s a real mouthful, so what that’s saying is we’re going to look at how the minerals look from the outside to determine how everything would have combined inside.
The overall shape or the habit of the mineral. We might sometimes get weird shapes and forms based on that.
Common terminology
We have the regular polygon shape. You get a cubic dodecahedron. Octahedrons that sort of thing now. For some other crystal habits, we have equipped which means that it’s equal in all directions, bladed fibrous tabular prismatic plastic blocky banded granular.
Luster
Under the next properties, we’re going to talk about the luster. This is the appearance of reflective light. We have two basic types: we have metallic and then you have nonmetallic. So metallic is pretty easy. It looks like metal. If it doesn’t that’s considered nonmetallic.
Color
We’re going to talk about color. It’s often an unreliable diagnostic property just because some examples of minerals can have a variety of different colors so you can have exotic coloration or inheritance. Color is typically one of the properties.
The color of a mineral in its powdered form is what we refer to as a streak. It helps to distinguish metallic Leicester. Metallic clusters typically have dark dense color streaks while nonmetallic ones tend to have lighter ones.
Hardness
We often look at the Mohs hardness scale and this is a relative scale.
Gypsum has a hardness of two on the scale. It’s not twice as hard as talc. Diamond is gonna be the hardest known substance and glass is going to be a five-point five and steel from a knife blade to be about six-point five.
Cleavage
If a mineral breaks in more than one direction you describe the number of directions and the angles that they’re meeting.
Specific gravity
So this can be estimated by the hefting of a mineral. There are a lot of other physical properties that we don’t get into.
Some of them are really useful, others maybe not. When we’re talking about elasticity, it’s to know how easily it breaks. Some minerals act as a Natural Monument and so they’ll attract metals to it.