Gemlike objects are a nearly ubiquitous phenomenon in the medium of glass, although culturally specific studies remain scarce. This dissertation considers the production of such works in the early medieval period, primarily in association with Abbasid rule. The first half attends to several accessory issues, including glass-related terminology, glass-coloring treatises, the lives of glassworkers, gemstone connoisseurship, and the legal status of such products. These demonstrate a range of coexisting attitudes, including the desirability of such works for their own sake rather than as surreptitious substitutes for “true” gemstones. The second half focuses on an exemplary object, an opaque turquoise glass bowl from the Treasury of San Marco in Venice, which I propose was produced in Baghdad for the caliph al-Mutawakkil just after the year 850. I then consider this work’s changing reception from late medieval Venice to modern scholarship, including ways in which “correct” interpretations of its material and/or origin have been repeatedly supplanted by false leads. The fundamental argument is that gemlike vessels like the San Marco turquoise were not deceptive stand-ins but rather intended to exercise complex discursive practices, both political and connoisseurial in nature, a function that ultimately remains in effect today.