Traditional Diwali diyas are typically made from clay.
These small oil lamps are usually shaped from earthen clay and kiln-fired before being sold, painted, or decorated. A cotton wick is placed in the lamp and soaked in oil or ghee. During Diwali, families light rows of diyas in homes, courtyards, temples, windows, and entrances.
The lamp’s glow carries several meanings: light overcoming darkness, knowledge overcoming ignorance, and good overcoming evil. In one widely told Hindu tradition, the people of Ayodhya lit lamps to welcome Rama, Sita, and Lakshmana home after Rama’s 14-year exile.
Clay is the typical answer, but not the only possible material. Ornate diyas may be made from brass, silver, stone, leaves, or other materials. This is why “typically” matters: a brass lamp is still a diya, but the familiar disposable festival lamp is generally earthenware.