Sorry, if my comment confused you. Yes, of course, if you can line up all your little cubes more or less perfectly, you will have preferred orientation! To do this is normally not very easy. Certainly with zeolites, where the crystallites generally differ in size and are most of the time also twinned and/or form aggregates, it is very unlikely to find such a situation. And cubic crystals do not necessarily need to crystalize as cubes, there are other forms possible. The "normal" ideal morphology for zeolite X is an octahedron, which, I would guess, are more difficult to align.
In short, yes, in special situations, you can get preferred orientation with cubic crystals, but I doubt, whether you will get this in a normal zeolite preparation. In any case, I think it is always a good idea, to check your powder particles under a microscope, to see how big the danger for preferred orientation might be.
Best
Christian
On Jun 3, 2004, at 4:06 PM, Stephen Hillier wrote:
Dear Christian (and others)------------------------
your reply about preferred orientation probabaly not being a problem with a cubic mineral is of interest to me.
This is something I have wondered about in the past because of observations I have made on common salt, so I thought I would contribute to this discussion in the hope that I can learn something. I am not a crystallographer so my thinking about this may be completely wrong, but if you pack a mineral like salt into a holder such that all the little cubes lined up (to some extent) in a regular way, would this show up as preferred orientation in an XRD pattern? or does it make no difference because the mineral is cubic? I pose my question because I have observed apparently different XRD patterns for salt when prepared in different ways. I guess my broader question is can cubic minerals show preferred orientation? I had convinced myself they can, your comments have now made me wonder about this again.
sincerely,
steve
Dr Stephen Hillier
Macaulay Institute
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Dr. Ch. Baerlocher
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