Genesis 19:24-26 Then the LORD rained upon Sodom and upon Gomorrah brimstone and fire from the LORD out of heaven; 19:25 And he overthrew those cities, and all the plain, and all the inhabitants of the cities, and that which grew upon the ground. But his wife looked back from behind him, and she became a pillar of salt.
The Hebrew word translated as salt in this passage is melach, which does indeed mean salt. However, the root of melach is malach, which means to vanish away, or dissipate, as salt does when mixed into water. Given that Hebrew writing omits vowels, it's easy to see why malach may have been mistranslated as melach. Here's a verse from Isaiah wherein malach (vanish away) is used.
Isaiah 51:6 Lift up your eyes to the heavens, and look upon the earth beneath: for the heavens shall vanish away (malach) like smoke, and the earth shall wax old like a garment, and they that dwell therein shall die in like manner: but my salvation shall be for ever, and my righteousness shall not be abolished.
While credit goes to Zecharia Sitchen for pointing out the melach/malach confusion, Zecharia didn't address the other word, pillar. But I have a theory about that. Recall the pillar of cloud/fire, which led the Israelites through the wilderness. What this term might be describing is a column of light which came down from heaven, perhaps much like this actual photo of a mysterious beam of light, which is but one of many contemporary examples wherein people have witnessed a beam of light being emitted from a UFO. Now returning to the story, we can theorize with some confidence that what might actually have happened to Lot's wife is that she became enveloped in a column of light (pillar) from above, and vanished away. One can't help but be reminded of Star Trek's transporter beam.
And it wouldn't be the first time such a thing happened in the bible. In the following passage, an unknown man who turns out to be an angel appears to Manoah and his wife, instructing them on how to raise their child. When he's ready to leave, a beam of light comes down to consume the sacrifice and the man steps into it and rises up to heaven!
17 And Manoah said unto the angel of the LORD, What is thy name, that when thy sayings come to pass we may do thee honour? And the angel of the LORD said unto him, Why askest thou thus after my name, seeing it is secret? So Manoah took a kid with a meat offering, and offered it upon a rock unto the LORD: and the angel did wondrously; and Manoah and his wife looked on. For it came to pass, when the flame went up toward heaven from off the altar, that the angel of the LORD ascended in the flame of the altar. And Manoah and his wife looked on it, and fell on their faces to the ground.
And with that, another amazing (and emerging) truth comes to light. For an in-depth discussion of this topic see also Steven Cheairs' excellent e-book, Lot's Wife. In that article he points out some of Jesus's words which lend additional weight to the theory that this was indeed a mistranslation, and that Jesus knew the actual meaning.
Also interesting is that the Hebrew word for angels is malachim. It would seem to me, therefore, that they were named after their ability to vanish into thin air.