The answer is HALITE, six letters. Halite is the mineral name for rock salt, the natural form of sodium chloride, and it is the only answer on record for this exact clue. The name is built on hals, Greek for salt, and that root also produces the neighboring entries most likely to trip you up.
A mineral name built from the Greek for salt
Despite its classical look, the name is a nineteenth-century coinage. The German mineralogist Ernst Friedrich Glocker coined it in Latin form in 1847, joining the Greek hals, salt, to the suffix -ite, and English had it by 1868. Rock salt remains its everyday name.
The same Greek root runs through a good deal of science vocabulary. Halogen, the name for chlorine and the other elements of its family, literally means salt-producer, because those elements form salts in their reactions. A halophile, from the Greek for salt-loving, is an organism that thrives in very salty conditions. The hal- at the front of all three words is the same salt.
Why the crystals come out as cubes
Halite crystallizes in the cubic system and splits cleanly along three directions at right angles, so even a broken lump tends to fall into smaller blocks. Pure crystals are colorless or white. Traces of other material can tint it light or dark blue, purple, pink, red, orange, yellow or gray.
Large deposits formed when enclosed lakes and restricted seas dried up and left thick beds of evaporite minerals behind, and some of those beds were later squeezed upward into salt domes. When crystals grow quickly, the edges of each cube can outpace the centers, leaving a stepped, hollow skeleton known as a hopper crystal.
HALIDE sits one square away
The most dangerous neighbor is HALIDE, also six letters and identical to HALITE except in the fifth square, where the T becomes a D. A halide is a compound of a halogen with a metal or a similar group, and sodium chloride technically is one, so the confusion is not even bad chemistry. It is simply the wrong word for a mineral. If the clue says rock, road or mineral, HALITE is the fill; if it talks about compounds or chemistry in general, check that fifth square before you move on.
Road salt wording leads to the same six letters, since the salt spread on winter roads is halite. And because this exact clue has only one answer on record, a six-square entry with this clue is one of the rare ones you can fill with no crossings at all.
Salt clues that want something else
| Letters | Answer | Clue wording |
|---|---|---|
| 3 | TAR | Old salt, meaning a sailor |
| 4 | NACL | Salt, chemically |
| 6 | HALITE | Rock salt or road salt |
| 6 | HALIDE | Chemistry wording, see above |
| 6 | SEADOG | Old salt |
| 8 | SEAFARER | Old salt |
| 8 | WATERDOG | Old salt |
Rock salt itself has only one answer on record, so this table is really a map of the traps around it. The sailor clues are the easiest to misread, because old salt has nothing to do with minerals; it means a seasoned sailor. NACL is the chemist’s formula for table salt, written in capitals with nothing between the letters. SEADOG and HALITE are both six letters, so a misread clue can put a sailor where a mineral belongs.
What rock salt does on a winter sidewalk
The rock salt sold by the bag is halite, and one of its main jobs is de-icing. Salt dissolved in water lowers the temperature at which that water freezes, so a scattering of it turns ice into brine that stays liquid below the normal freezing point. Old hand-cranked ice cream makers put the same effect to the opposite use. The canister sits in a mix of ice and rock salt; the salt melts the ice and pulls the temperature of the brine below freezing, and that cold is what slowly freezes the cream.
Halite has kitchen jobs too. It is used in cooking as a flavor enhancer and to cure a wide variety of foods, so the mineral in this clue is, chemically, the same sodium chloride that sits in a salt shaker.
