An oil lamp, cost 10, is a light source. Applying one will provide light to darkened areas for 1000 to 1499 turns. They can be refilled with scrolls of charging or potions of oil (using the #dip command). If you dip a lit oil lamp into a potion of oil, you are likely to cause a fireball.
When you release a djinni from a magic lamp, the lamp becomes an oil lamp.
It's a good idea to name oil lamp by class, when you're sure it's regular oil lamp; this way you can distinguish it from magic lamps met on your way.
If an oil lamp is cursed, it might not light when applied.
The following classes can start with an oil lamp: