Talk:Cleavage (crystal)

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Images[edit]

Some images of the different types would be helpful.

He's right, some pictures would be very helpful.
Added a picture of biotite with basal cleavage. Unfortunately, Wikimedia commons doesn't have many good crystal cleavage pictures, and this isn't quite high enough on my priority list to go hunting everywhere for openly available photos. Awickert (talk) 17:32, 30 November 2008 (UTC)

Miller index[edit]

I changed this sentence:

"Basal or pinacoidal cleavage occurs parallel to the base of a crystal, the {001} crystal plane."

I replaced {0001} with {001} because I have only seen a Miller index with three digits (indices), not four, representing the three planes in 3D space. However, I see later in the section a four-digit Miller index for faces of a rhombus or rhombohedron, so that's an example of a 4-digit Miller index. Was the original 4-digit Miller index correct? Is it generally possible to have 4-digit Miller indices? Crystal whacker (talk) 00:02, 26 November 2008 (UTC)

The hexagonal and rhombohedral systems use four indices (see Miller_index#Case_of_the_hexagonal_and_rhombohedral_structures. I've replaced the {0001} along with the {001} with a clarifying note. Thanks for noting that as the {0001} by itself was misleading. Vsmith (talk) 00:29, 26 November 2008 (UTC)
(Vsmith beat me to hitting "save".) Standard Miller indices only have 3 entries, but in hexagonal and rhombohedral structures, Bravais-Miller indices (with 4 entries) are often used. You can check it out on Miller index. I think your edit should stand because it makes the basal cleavage more generalizable and therefore more correct: muscovite, one of the best examples of basal cleavage, is actually monoclinic. Awickert (talk) 00:31, 26 November 2008 (UTC)
Wow, I didn't know that hexagonal crystals could have 4 Miller indices! Thanks for explaining that. Crystal whacker (talk) 00:35, 26 November 2008 (UTC)
Yeah - funny, huh? but it works more intuitively (for some people) for hexagons - for semantics they're called Bravais-Miller indices to separate them from standard 3-directional Miller indices. Awickert (talk) 00:52, 26 November 2008 (UTC)
Kept the {0001} in as one example given, graphite, is hexagonal. Probably could be worded better. Vsmith (talk) 02:55, 26 November 2008 (UTC)
Re-worded basal cleavage to include links to Miller Indices - it's now wordy, but hopefully it will help, as it's the first example of them in the article and I can imagine that not everyone looking up mineral cleavage knows about crystallographic notation for planes. Awickert (talk) 22:49, 26 November 2008 (UTC)

No introduction[edit]

The text starts without any introduction or explanation regarding what is a cleavage in crystals. It just starts with a listing. — Preceding unsigned comment added by 212.235.77.210 (talkcontribs) 11:22, 26 June 2013

Fixed old vandalism from May. Thanks for noting the problem. Vsmith (talk) 13:14, 26 June 2013 (UTC)