Halite

Halite (from ancient Greek ἅλς hals, Gen. ἁλός halos, "salt") is a common mineral in the mineral class of simple halides. It crystallizes in the cubic crystal system with the chemical composition NaCl and is thus chemically sodium chloride.

Halite usually develops cube-shaped crystals and large, granular to massive, rarely also fibrous mineral aggregates. In pure form halite is colourless and transparent. Through multiple light refraction due to polycrystalline formation, however, it can also appear white and take on a grey, brownish, yellow to red or bluish colour due to foreign admixtures or lattice structure defects, whereby the transparency decreases accordingly.

Halite is a rock-forming mineral and plays a significant role in the formation of rock salt deposits. Rock salt is a monomineral rock which, except for small admixtures of other salt minerals such as anhydrite, gypsum, sylvin and others, is composed almost exclusively of the mineral halite. Therefore, "rock salt" and "halite" are often used synonymously in German colloquial language, despite their inaccuracy.

Etymology and history

The name halite is derived from the ancient Greek word hals ἅλς (plural hales ἅλες, neuter halas ἅλας) for salt and the suffix -itos -ιτος and thus means "salty" or "pertaining to salt" (see also halogens).

Table salt extracted from salt domes or salt works has been a coveted commodity since antiquity and was exported on so-called salt roads from the places of production to regions with low salt content. In some cases it had such a high value that it was also referred to as white gold.

Classification

Already in the outdated, but partly still used 8th edition of the mineral systematics according to Strunz, halite belonged to the mineral class of the "halides" and there to the division of the "simple halides" (with metal : halogen = 1 : 1), where it formed as eponym the "halite series" with the system no. III/A.02 and the further members bromargyrite, carobbiite, chlorargyrite, sylvin and villiaumite.

In the Lapis mineral directory according to Stefan Weiß, which out of consideration for private collectors and institutional collections still follows this classical systematics of Karl Hugo Strunz, the mineral received the system and mineral no. III/A.02-30. In the "Lapis systematics" this also corresponds to the section "Simple halides", where Halite together with Bromargyrite, Carobbiite, Chlorargyrite, Griceite, Sylvin and Villiaumite forms an independent, but unnamed group.

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, classifies halite in the somewhat refined division of "Simple halides without H2O". This is further subdivided according to the molar ratio of metal (M) to halogen (X), so that the mineral is to be found according to its composition in the subdivision "M : X = 1 : 1 and 2 : 3", where it also forms the "halite group" with the system no. 3.AA.20 and the further members carobbiite, griceite, sylvin and villiaumite.

The system of minerals according to Dana, which is mainly used in English-speaking countries, also classifies halite in the class and eponymous division of "halides". Here it is also to be found in the "halite group" named after it with the system no. 09.01.01 within the subdivision "anhydrous and hydrous halides with the formula AX".