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This can be tricky for some specimens as colours can vary in intensity and often fades in dead, empty shells. The colour is enhanced, and slightly altered by the periostracum, the shiny, almost varnish-like outer layer on the outside of a fresh shell. It is made of material very similar to your fingernails! This gradually peels off empty shells, and may get lost even in living snails, especially if they have lived a long time, or if they are in a habitat where there is a lot of abrasion (snails living in sand dunes get literally sand-blasted).
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