When was glass invented?

People had used naturally occurring glass, especially obsidian (the volcanic glass) before they learnt how to make glass. Obsidian was used for production of knives, arrowheads, jewelry and money.

The ancient Roman historian Pliny suggested that Phoenician merchants had made the first glass in the region of Syria around 5000 BC.

According to the archaeological evidence, the first man made glass was in Eastern Mesopotamia and Egypt around 3500 BC and the first glass vessels were made about 1500 BC in Egypt and Mesopotamia. For the next 300 years, the glass industry increased rapidly and then declined.