Discusses the largest bank of compositional data yet assembled for Early Christian (6th-10th century) Irish glass. The material studied was transparent and opaque and was analyzed using electron probe x-ray microanalysis (EPMA) and scanning electron microscopy (SEM). The data for transparent glass offers the possibility of assessing the extent to which the glass was recycled. The crystalline inclusions in opaque glasses including those on glassmaking crucibles have been studied using SEM. -- AATA