Glassteine mit blauen Einschlüssen: Zu einem besonderen Typ mittelalterlicher Glassteine und anderen gläsernen „Edelsteinen“

The numerous glass stones coexisting with precious or semi-precious stones on many medieval objects have been mostly neglected by scholars to date. Often they are difficult to distinguish from natural stones, and if their material is recognized as glass, they are regarded as cheap substitutes (or even fakes) and suspected to be added some time later. But there is a special type of glass gems which are without a doubt medieval: those made of colorless glass with blue inclusions. Such glass stones were probably made somewhere in the northwest of present-day Germany because they are found almost exclusively on objects made in those regions during the eleventh through thirteenth centuries. So, the blue-spotted gems are key pieces for our understanding of at least some aspects of the production and use of medieval glass stones.