Why doesn't it cleave nicely along the (100) or (010) or any other planes? What determines its cleavage plane? I know it has something to do with the fact that it crystallizes in face centered cubic system but I don't understand why things happen the way they do.
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$\begingroup$ Fun fact: I keep getting up-votes but no answers. $\endgroup$ – Tamás Jun 1 '14 at 18:24
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$\begingroup$ I think the fcc that you mention is the key. I can imagine it in my head, but hard to explain. Try drawing an fcc crystal on paper and plotting the 110 plane - it will cut diagonally across the side of the face-centered cell. By extrapolation, I would also expect cleavage on 101 and 011 planes. $\endgroup$ – winwaed Jun 2 '14 at 13:40
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$\begingroup$ According to mindat.org it has perfect cleavage on {001}. Do the curly brackets include those planes mentioned by you? $\endgroup$ – Tamás Jun 2 '14 at 15:36
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$\begingroup$ Yes. So where did you get the (110) from? $\endgroup$ – winwaed Jun 4 '14 at 19:49
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$\begingroup$ My mineralogy professor who has a PhD in geology... Don't ask $\endgroup$ – Tamás Jun 5 '14 at 8:28
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I think the commenters have identified the issue. Halite does not have perfect cleavage along the {110} plane. As recorded in Mindat, Halite has perfect cleavage alone {100}, {010}, and {001}. This makes sense, as Halite is a cubic mineral (fcc), these are the planes you would expect it to cleave on.
