[Leica] Fossils and Minerals - help!

[DouglasMSharp at netscape.net (Douglas M. Sharp)]

I've been trying to get some decent shots of fossils and stuff I collected 
in 
the UK over the past couple of years. Somehow they just don't seem right to 
me.

Any suggestions please on a) lighting
                           b) backgrounds
                           c) point of focus - front, middle or ???

Taken with a Leica Macro-Elmarit 100/4 at f16

I've seen transparent crystals shot against black velvet backgrounds and 
they 
seem to have an "inner light" how do I get this effect?

Would very much appreciate any ideas, hints or references.
Douglas

http://gallery.leica-users.org/New-Old-Pictures/pyrites2
Iron Pyrites with natural lighting from left, artificial from back right.

http://gallery.leica-users.org/New-Old-Pictures/Pyrites_copy
Iron Pyrites with natural lighting from left, artificial from back right.
b/w version

http://gallery.leica-users.org/New-Old-Pictures/Ammonites_copy
Bedded ammonites (8mm diameter) lit from top left, normal room lighting.

http://gallery.leica-users.org/New-Old-Pictures/ammonite
cross-section of a filed chamber in an ammonite fossil, daylight from left

http://gallery.leica-users.org/New-Old-Pictures/ammonites
Raw and cut and polished ammonites - showing external and internal structure
daylight from left

http://gallery.leica-users.org/New-Old-Pictures/urchins

with this last shot I'm trying to show the similarity of a fossilised sea 
urchin
and a modern one. I've tried all sorts of angles and lighting but it is 
always 
just dead boring. It just doesn't work.