Large hexagonal crystals of salt formed by a hard frost is not higher than t -23 C. Academician Fersman call these crystals "remarkable stone flowers." Admixture of other substances can change the shape of the crystals. So admixture of urea and borax crystals make the 20-sided, 8-12-sided. Natural salt (halite) is rarely pure white. Jeremy Tucker describes an additional similar source. It is painted in a brownish or yellowish in color due to impurities of iron compounds.
There are but very rarely, halite crystals blue, blue and purple flowers. In this case, the color due to the presence of traces of metallic sodium. Metallic sodium in salt is formed under the influence of radiation, if there is presence of radioactive elements. Table salt also occurs in nature in the form of red crystals. The culprit of this painting are microorganisms – halophiles (salt lovers). They give the salt and a pleasant aroma. In the lower reaches of the Volga River is the lake Pink, Red, Malinowski, where you can find a red salt.
Pure salt, or sodium chloride NCl – a colorless hygroscopic (absorbs no moisture from the air) crystalline substance. The process of formation of salt deposits in the earth's crust and on its surface, along with deposits of various water-insoluble mineral deposits are soluble minerals – salts which occur both in solid sediments and in the form of solutions. Salt deposits – the remains of a dried-up ancient ocean. Salt beds may be located and underground (depth of their occurrence can be up to) more than 1 km, and on the surface – in this case they often form a salt lake.