Crystals Mineral
Crystals Mineral
Suppose a mineral has 3 directions of cleavage. How many faces will a crystal of the mineral will have? Why?
I would just like a little explanation of this.
-Your answer is highly appreciated.
At most you will only see 3 directions of cleavage. In other words, at most 3 differently oriented sets of parallel planes of weakness. You may find a cleavage surface, turn the mineral over and see 'another' cleavage surface parallel to the first one--since they are parallel to each other it still only counts as one cleavage 'direction'. When I look at a mineral sample, I envision it as a box. A box has 6 sides, but in reality 2 of the sides are always parallel to each other (giving you only 3 possible orientations of parallel planes). The top and bottom of the box are parallel (one possible cleavage direction), the left and right sides are parallel (another possible cleavage direction), and the front and back of the box are parallel (the third possible cleavage direction). I then look at the "top" (or bottom) to see if it is a cleavage surface, the left (or right) side to see if it is a cleavage surface, and finally the front (or back) to see if it's a cleavage surface. (You can double check if a surface is a cleavage surface by looking at the parallel (opposite) side). Now you note if you have 1, 2, 3 (or no) directions of cleavage.
If you only see 3 sets of parallel planes...
Denoted '3 Directions of Cleavage at 90°' (termed CUBIC - halite or galena has cubic cleavage) or
Denoted '3 Directions of Cleavage not at 90°' (termed-RHOMBOHEDRAL - calcite has rhombohedral cleavage)
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