1) How many sides do crystals of each of the 6 major crystal systems have?
http://www.geocities.com/asdfasdf23135/crystalsystem1.GIF
http://www.geocities.com/asdfasdf23135/crystalsystem2.GIF

I am really puzzled when by this question, since I can see two completely different shapes on the above 2 diagrams that I obtained from 2 different sources. For example, orthorthombic system on the top only has 6 sides while the bottom one has 14 sides (I think). Which one is right?

2) How would you use crystal structure to tell a crystal of pyrite from a crystal of gypsum?
The problem is I do not know whether "crystal structure" and "crystal system" are the same thing...I searched google definitions but I don't get what they mean
If so, the answer is simple -- cubic for pyrite and monoclinic for gypsum

3) I have learned that most crystals are restricted by its surroundings so large crystals usually can't grow. But do minerals still tend to appear in one of the 6 well-defined shapes? I mean, will they still develop into these nice, well-defined shapes?


Does anyone know??

HI, can anyone explain?

1. What is a side? If you know that, then you should be able to answer these.

2. Note: pyrite can also take on a dodecahedral form, although I'm not sure if it technically belongs under another sort of category, and not all feldspars are triclinic. That's all.

1. What is a side? If you know that, then you should be able to answer these.

2. Note: pyrite can also take on a dodecahedral form, although I'm not sure if it technically belongs under another sort of category, and not all feldspars are triclinic. That's all.
1) The thing is I found that the 2 figures contradict each other. For example, orthorthombic system shown on the top only has 6 sides while the bottom one has 14 sides! The hexagonal system on the top has 8 sides and the bottom one of the same system has 18 sides. They are inconsistent, why is it like that?? strange......

I'm not an expert on mineralogy, but experience with this tells me that you sort of exclude small nicks and insignificant sides when dealing with the main crystal structure.

What I noticed is that you can also just pay attention to the sides that don't change on opposite faces of the crystal, and then leave out everything else. For example on the monoclinic drawing you can see trapezoids that don't match on opposite sides, so you can judge the axes from the two rectangular prism faces, which is practically identical to the model given above.

^^ Actually, I retract the latter on the last post. Doesn't work for a lot of shapes.