Crystals and phase transitions in protohistoric glass materials

This article reviews the crystalline material present in representative Bronze Age glasses and glassy materials from Northern and Central Italy. Their nature and formation processes are discussed based on textural, crystallographic, and chemical data. Distinction is made between crystals present in the starting raw materials and left unreacted during the glass production process, crystalline phases deliberately or accidentally formed during manufacturing, and crystalline phases added in the last stages of glass working to change the macroscopic properties of the final material. It is argued that in Bronze Age Italy glass production technology was advanced and well mastered so to produce materials having unique characters of colour and workability.