So, most rocks on earth are made up of silicates, and silicates come in 5 basic flavors; Olivines, Pyroxenes, Amphiboles, Micas, and Quartz.
The basic structure of silicates are the silicate tetrahedron. This is a 3-faced pyramidal structure that has one silicone atom at its center, surrounded by 4 oxygen atoms at each corner of the pyramid. All silicate minerals have this structure at it's base. The silicone has a +4 charge, and each oxygen has a -2 charge. This means that each oxygen atom takes up one of the positive charges of the silicone, and still has a negative charge left over to bind with other positive atoms at each corner of the tetrahedron.
We start off with Olivines (SiO4 -4 charge), which come in two primary flavors; Fayelite, and Forsterite. Olivines are rocks where the silicon tetrahedrons are not connected to other tetrahedrons. Fayelite is connected to iron (Fe2+), while forsterite is connected to magnesium (Mg2+). Fe2+ and Mg2+ are very similar in size and mass, and have the same charge, so they are interchangeable, and can act as a connecting point to other negatively charged elements, or other silicate tetrahedrons (since they have a -1 charge free on each corner). It is probably impossible to find a natural olivine that is pure fayelite, or pure forsterite, so these words are more of a scalar definition (if it's mostly iron, then its fayelite, and vice versa).
When we look at the structure of a silicon tetrahedron, we see that it is possible to have two silicons attached to the same oxygen. If two tetrahedrons share a corner with each other we have Si2O7. If we make a chain out of these tetrahedrons, connecting them corner to corner in a line, then we have a pyroxene. In the image below, the point of view is looking at a pyroxene chain from above, so the dots in the center of the triangles that say top are the tops of the pyramids.
Since pyroxenes are long chains of tetrahedrons attached at two corners (except for the ends, where only one corner is attached to another tetrahedron), that leaves two corners of the tetrahedron available for attachment to other tetrahedra. If we attach three corners, then we get two chains that are linked in the center. These are called amphiboles (like everything else in geology, no matter how you are pronouncing it, you are pronouncing it correctly [I told my gneiss to have a gneiss day]). Amphiboles have one free corner on the inside track of the chains, and two free corners on the outside track. Again, the following image is a view from the top.
At the macro (hand sample) scale, amphiboles and pyroxenes are often hard to tell apart. They are both long minerals that tend to have darker coloration. The best way to differentiate them is to look "down the barrel" of the mineral. Pyroxenes favor 90° angles, while amphiboles are more rhombohedral with a 60°/120° angle.
What happens if we make a flat sheet out of tetrahedrons? Glitter happens, Literally. Micas are the mineral that glitter was made from before the advent of plastic. It is a flat, shiny mineral that forms in flat sheets that is easily pulled apart. I'm linking to an image of a hand sample of muscovite, a silvery colored mica that is sometimes used in the construction of blast furnace windows (it is a good insulator that is also somewhat transparent).
Next is a picture showing the sheet structure of the tetrahedrons again, looking down from the top:
Last but not least are the framework silicates. Quartz is the mineral that is formed when all of the silicate tetrahedra are attached to each other. Quartz is much much harder than mica. Pure quartz is clear, and forms naturally in a crystalline pattern that terminates in a point. It is probably the mineral you first think of when someone says crystal.
Inclusions of other minerals (rose quartz), or radiation damage (smoky quartz) can change the color of quarts, and other minerals can grow inside of quartz (such as rutile).
That's it for silicate minerals. I think next I am going to go over Bowen's Reaction Series since it directly ties into how these minerals form.