What is the meaning of negative and positive forms that can make up a crystal mean?

Question

I read Quartz for instance can be comprised of rhomborhedral units that are positive and negative forms (or first or second order). What does all this mean? Any help appreciated.

Answer 1

This probably isn't what you are looking for but most crystals are  left handed compared to right handed. Two crystals can look almost the same but if you superimpose one over the other you will see they will not match the other. (opposite) - Left handed to right handed. Most know life is left handed crystalline.

Hope this was some help.

Answer 2

It's explaining the chemical make-up of quartz.  The atoms are arranged in a rhombohedral shape, with the bonding either in first or second order.  I think that the other answerer explained the left/right isomers better than I could.  This is stuff that you would probably learn about in a chemistry (2nd semester) or mineralogy course.