gems, natural glass, moldavite, Czech Republic, tektite, Bohemia, Moravia,

This paper surveys natural glass occurrences with a focus on materials of gemmological interest. The first section covers tektites, particularly gem-quality moldavites, presenting new geological insights and gemmological uses. The second part inventories all known or suspected natural glasses, highlighting unusual specimens but emphasizing those most relevant to gemmology. It also notes that some visually appealing glasses remain unused in jewelry because their natural origin cannot currently be verified.