A hard, amorphous, inorganic, usually transparent, brittle substance made by fusing silicates, sometimes borates and phosphates, with certain basic oxides and then rapidly cooling to prevent crystallization. It was first developed from faience about 4,000 years ago in the Near East, but was rarely used for anything larger than beads until Hellenistic and Roman times. Glass bottles in Egypt are represented on monuments of the 4th Dynasty (at least 2000 BC). A vase of greenish glass found at Nineveh dates 700 BC. Glass is in the windows at Pompeii and the Romans stained it, blew it, worked it on lathes, and engraved it. Natural glasses, such as obsidian, are rare, but cryptocrystalline materials, with fine crystal structures somewhat like glasses, are relatively common (e.g. flint).