Two glass beads found at Nippur, south of Baghdad in lowland Iraq, are the world's oldest extant glasses. They were found in sealed floors in association with cuneiform tablets in an Akkadian level (ca. 2350 BCE) and prove that glass technology dates to the late 3d millennium, rather than the mid-2d millennium BCE as was once commonly believed. One bead, a brilliant, translucent, yellow-and-bluish-green barrel bead with a hexagonal cross section, is a one-of-a-kind example, made of a lead oxide-tin oxide-calcia-magnesia-phosphate-silicate composition containing six crystalline phases and a microstructure unlike those of any later glasses colored with lead compounds. This bead may have been derived from metallurgical slags related to lead and tin processing. Lead isotope analysis shows that a probable source of these materials is the Taurus Mountain of south-central Turkey. The other bead is less well-crafted and probably was made locally from available materials at or around Nippur. This spherical bead is opaque white and transparent olive-green and is made of a soda-lime-silica composition similar to most of the glass produced today. Differential thermal analysis and replicative studies show that both beads were formed around rods, by fusing and paddling bits of glass at a temperature which did not exceed 900°C in a highly viscous state similar to that of warm wax, about 10 poise.