Armel,
We use a gadget marketed by McCrone that is not a ball mill, but has small,
cylindrical elements. (It's relatively inexpensive, ~2500$US, I think.)
These can be of either agate or alumina. There are 56 elements close packed
in a canister w/ a capacity of ~100 mL. We use these w/ ~2 gm of sample and
either wtr or propanol. 5 to 10 min of shaking yields a powder w/ a small
range in particle size. Depending on the amt of time of grinding, that size
is 1 to 5 �m, and no degradation of xl structure. Then we side load these
powders, w/ gentle packing. In our tests of this procedure, preferred
orientation of minerals w/ good cleavage, like calcite or feldspars, is
completely or almost completely eliminated. I think it would be worth a try
on biotite.
Perhaps you should separate the biotite and study it separately. You can
learn an awful lot from an oriented aggregate. One of the few advantages of
hkl peaks of micas is to identify the polytype, but, unless you have
something unusual, the biotite is going to be 1M, and it's going to be
trioctahedral so you don't really need the (060). One can also correct for
perferred orientation. I think Reynolds treated this in Clays and Clay
Minerals 34:359-367 (1986).
Steve Hillier at the Macaulay Inst in Scotland has described a way to do
spray drying that doesn't require expensive equipment. He says that it
should be published inthe next issue of Clay Minerals. He said that
12/11/98. And then there's freeze drying. That's what we used for the
article: Grathoff, G.H., and Moore, D.M. (1996) Illite polytype
quantification using WILDFIRE� calculated patterns: Clays and Clay
Minerals, 44, 835-842. But this does require some equipment.
Hope this helps,
Dewey
______________________________________________________________
D.M.Moore, Senior Clay Mineralogist Ph (217)244-2529
Illinois State Geological Survey Home Ph 328-7507
615 E. Peabody Dr FAX
(217) 244-2785
Champaign, IL 61820
