Hi Carol
 
I think a lot of people consider a "gem" specimen suitable only for a
personal collection, this leads to much overcollectiong particularly for
species with a heavy periostracum in order to obtain such a shell. This
then leaves plenty of specimens, which are not of such a quality.
Presumably these shells are considered "Museum quality", the sooner we
get over this mentality and accept a good quality specimen for our
collections and shun the term gem, the better for malacology and our
concience.
 
Kev