Since 'magical gem' is a category of modern archaeology, category boundaries are not very strictly set and followed in The Campbell Bonner Magical Gems Database. As a rule, the database distinguishes between five categories: magical gems, magical(?) gems, amulet gems, amulet(?) gems and votive gems. The primary focus is naturally laid on magical gems, while pieces in the magical(?) gems group are also invariably selected. We do not integrate all amulet and amulet(?) gems; exceptions are made, however, when these appear in selected publications (such as Bonner, SMA or Michel, BM) or belong to collections with restricted access (see for example our selection of gems from the Visegrad countries and the Zeugma impressions).