Salt domes contain anhydrite, gypsum, and native sulfur, in addition to halite and sylvite. Nonporous caprock such as halite (rock salt) or anhydrite is more effective in trapping helium. The halite (salt) is removed first, leaving behind gypsum and anhydrite. It is often accompanied by anhydrite, carnallite, halite, and kieserite. It occurs in association with halite, gypsum and celestine in the California dry lake. It occurs in association with trona, thermonatrite, thenardite, halite, gaylussite, burkeite, northupite and borax. Common examples of halides include halite (NaCl, table salt), sylvite (KCl), fluorite (CaF). Other solid deposits include halite, amphibole, cryolite, nitratine, and zeolite. Halite (rock salt) is produced as a byproduct of potash mining. Sylvite, along with quartz, fluorite and halite, is used for spectroscopic prisms and lenses. Halite deposits are often mined for use as salt. Beneath the layers of sediment is a water-deposited layer of halite, a rock salt. Halite, NaCl, is table salt; its potassium-bearing counterpart, sylvite, has a pronounced bitter taste. Many salts are halides; the "hal-" syllable in "halide" and "halite" reflects this correlation. Evaporite formations need not be composed entirely of halite salt.