Salt lamp

Salt lamps are blocks of salt with either electric lights or candles inside that are claimed to improve one's health by releasing negative ions into the air. They don't do that, of course, and the only proven benefit to owning a Himalayan salt lamp is that it can be nice to look at.

"Himalayan" salt
Salt lamps are marketed as being made of, probably in order make them seem more New Age-y and spiritual. After all, Himalayan crystals must be chock full of mystical healing energy, as opposed to those mundane Western sodium chloride rocks, right? Actually, the term Himalayan salt is a bit of a misnomer, as it refers to salt from the Pakistani Khewra Salt Mine, which is nowhere near the Himalayas.

Negative ionic goodness
The problem with the claim that these lamps release negative ions is that electric lights and candle flames aren't nearly hot enough to break apart the ionic bonds between sodium and chlorine. As one university physics professor puts it, "If that were true, we'd have chlorine gas coming out our salt shakers." The electrostatic attraction between even two ions is so large that chloride cannot be released in significant amounts. The orange color that they emit is from the excitation of electrons to higher energy levels. They are orange because of impurities in the salt, especially iron oxide (rust). If fire can't make these lamps release negative ions, it's not likely slightly warm electric lights could.

Perhaps these lamps don't ionize the sodium or chlorine in the salt, but the molecules in the air around the lamp. "Negative ions" have been a buzzword used by various woo machines for decades, and there do exist air ionization machines that can indeed negatively ionize air molecules. The only problem is, negatively ionized air molecules don't really cure anything. (If you have a lot of ions in the air, we call it "lightning.") Whether salty air does anything is of course another thing entirely, but one would imagine ancient sailors wouldn't keep dying of everything if there were some secret magical healing quality to it.

Practical Uses
Salt Lamps make a good conversation piece and a half-decent night light so you don't step on your cat on your way to the bathroom at 2 AM.

The lamps are also useful as a salty popsicle, if for some reason you like salty popsicles.

They also tend to be a reddish-orangish colour, which means they emit less blue light than more whitish lamps (that is, they have a lower colour temperature, if you know what that means). So you may end up sleeping a little better than you would with a brighter, more whitish-coloured lamp. Of course, there are other ways of achieving that effect.

You might also be able to chip some shavings off it, if you ever run out of salt and need more. That's about it.