Himalayan salt lamps are made from pure himalayan salt rocks. Salt lamps emit negative ions. The bulb inside of the lamp heats the crystal and supports the ionizing effect. Salt itself is hygroscopic and attracts water from the surroundings. You can often see that the lamp is damp or even wet, especially in more humid environments. Due to the gentle heat of the lamp, the water quickly evaporates and during the evaporation process the beneficial negative ions get created.