Ammonite is the fossil that you are referring to. It is a mineralised
fossil and are often the calcite casts of the interior of the ammonite
shell. Sometimes the shell is replaced by iron pyrites and the inside
filled with greenish calcite. A lot of these have been found in Lias of
Dorset in England.
A number of ammonites found in the Western States of America have the
septa filled with crystals and small specimens of these are split into two
and the cut surfaces are polished beautifully to produce articles of
Many articles have been written in the Lapidary Journal specifically on
ammonites and other fossils and their use in jewellery. You can see issues
October 1997,June 1991, July 1992, July 1994. There is a particularly good
article called “Ammonite Artistry” by Cathleen McCarthy on page 46 July
1992 issue of the Lapidary Journal I am sending you a scanned image of an
example of ammonite use in jewelry. I don’t know if images like this are
allowed to be posted in this forum so I am sending it to you directly. In
case anyone else wants to see it let me know off the board and I can do
Hope this helps !
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