A less poetic view: The conical lamps contain a watery fluid and the "lava."

Newer lamps contain less mercury and the 3-4 mg versions are sold as low-mercury types.

Each lamp contains a small amount of mercury, which must vaporize to support the lamp current and generate light.

The lamps are coated on the inside with special phosphors and contain a small amount of mercury (20 mg typical).

Besides the mercury vapor, the lamp contains iodides or sometimes bromides of different metals.

Since a metal-halide lamp contains gases at a significant high pressure, failure of the arc tube is inevitably a violent event.

All fluorescent lamps contain mercury, and at this time, no suitable replacement has been found.

It happened once that a lamp of this character - a simple jar hung with a wick - contained only enough oil to last a single day.

Fluorescent lamps contain mercury which is released when bulbs are broken.

Halogen lamps do not contain any mercury.