Halite

Halite ( Ancient Greek ὁ ἅλς, ἁλός "salt" ) is a commonly occurring mineral from the mineral class of simple halides. It crystallizes in the cubic crystal system with the chemical composition of NaCl ( sodium chloride) and usually develops cubic (block -shaped ) and large crystals, granules to moderate, rarely fibrous aggregates. Pure halite is colorless or white microcrystalline training. By incorporation of the hematite crystals take on a red color, with incorporation of a yellow limonite. By admixtures of clay minerals or bitumen halite appears gray to brown. Lattice defects in the crystal structure generated by interference ( overlay by diffraction of light rays ) a bluish tint.

Halite is a rock forming mineral and instrumental in building the rock salt deposits. Rock salt is a mono- mineral rock, which, composed, except for small amounts of other salt minerals such as anhydrite, gypsum, sylvite and other, almost exclusively from the mineral halite. Therefore, " rock salt " and " halite " are often used interchangeably in everyday German despite inaccuracy.

Special Features

Under UV light, show some Halite red fluorescence.

Etymology and history

The name derives from the ancient Greek halite word ἅλας [ neck ] for salt and the ending- ιτος [- itɔs ] and accordingly is salty or concerning the salt (see also halogens ).

The salt obtained from salt mines or salt pans since antiquity a coveted commodity that was exported to the so-called salt streets of the manufacturing sites in low-salt regions. It had partly such a high value that it has been referred to as White Gold.

Classification

In the 8th edition of the now-obsolete Strunz'schen Mineral classification of halite still belongs to the combined department of the " Simple halides ". This department has been expanded with the revision of the systematics in the new, 9th edition and precision divided by Formelbau, crystal water content and molar ratio of the ions involved. Accordingly, the mineral is now in the sub-division of a "Simple halides, without H 2 O and the molar ratio M ( etal ): X = 1: 1 and 2: 3" to find where it together with Carobbiit, Griceit, sylvite and Villiaumit the unnamed group 3. AA.20 forms.

The mostly commonly used in English-speaking classification of minerals according to Dana sorted the halite in the, opposite the new Strunz'schen systematics somewhat simplified, Department of " water clear and hydrated halides with the formula AX", where he served as Leitmineral the Halitgruppe with the other members sylvite, Villiaumit, Carobbiit and Griceit forms.

Education and Locations

Halite occurs in massive, granular or crystalline form in sedimentary rocks. It is formed by crystallization of seawater and is in the resulting deposition layers ( evaporite ) associated with other less water-soluble minerals calcite and anhydrite. Anhydrite Ca [ SO4 ] emerged from the originally crystallized gypsum Ca [ SO4 ] 2 • H2O by dehydration. Rock salt deposits that were sunk deep, behave plastically deform under pressure and often to huge structures, salt walls or salt domes. It is rare to rock salt as a sublimate in volcanic vents or fumaroles among other things on Etna and Vesuvius in Italy.

Worldwide, Halit so far (as of 2010 ) can be detected at around 300 localities, so include Afghanistan, Algeria, Antarctic, Argentina, Ethiopia, Australia, Azerbaijan, Belgium, Bolivia, Bosnia and Herzegovina, Brazil, Chile, China, Denmark, Germany, Dominican Republic, Djibouti, Finland, France, Greece, India, Iran, Iceland, Italy, Japan, Kazakhstan, Kenya, Colombia, Democratic Republic of the Congo, Morocco, Mexico, Namibia, Netherlands, New Zealand, Norway, Austria, Pakistan, the entire region of Palestine (Israel, Golan Heights, Gaza Strip, West Bank and Jordan), Panama, Peru, Poland, Portugal, Romania, Russia, Saudi Arabia, Sweden, Switzerland, Serbia, Slovakia, Spain, South Africa, Syria, Tanzania, Tunisia, Turkey, Turkmenistan, Ukraine, Venezuela, the United Kingdom ( UK), the United States ( U.S.) and Belarus ( Belarus). Outside the earth, the mineral could still be detected on the Moon in the rock samples of the Mare Crisium.

Significant Locations in Central Europe is the huge salt deposits from the Upper Permian ( Zechstein ) underground in northern Germany ( " Zechstein " ), some with potassium salts. Extraction of rock salt is still taking place at Bernburg, earlier example in Strassfurt. On this point, the middle Muschelkalk in Baden- Württemberg rock salt layers ( Heilbronn, Stetten in the Swabian Alb), which continue to Switzerland ( Rheinfelden, Switzerland hall, especially powerful drilled at Pruntrut). In Austria, mention Bad Aussee (Styria ) and earlier Hall (Tyrol ), Hallein (Salzburg) and Hallstatt ( Salzkammergut). Become famous is the salt mine in Wieliczka Poland. The largest salt crystals in the world with edge lengths of about 90 cm are found in the crystal cave in the Adventure Mine in Thuringia.

Crystal structure

Halite crystallizes in the cubic space group with the several measurements obtained from the year 2004, the average lattice parameter a = 5.70 Å and four formula units per unit cell.

The NaCl type structure composed of an ionic lattice with two interpenetrating and staggered by half a edge length flächenzentierten cubic crystal lattices. Each sodium cation is octahedrally also octahedrally surrounded by six chloride anions, and each chloride anion of 6 sodium cations. This type of crystal structure by ionic bonding also explains the low hardness and perfect cleavage and brittleness, firstly because the binding forces of the relatively large ions are only weakly and on the other hand even at low shear stress ions with the same, to meet repulsive electric charge and the crystal to the spot drift apart. Its crystal structure is isotypic with galena.

Use

The halite extracted from rock salt, as used in other ways obtained, sodium chloride, as a table salt, road salt, in the food industry and in medicine. It is therefore of great economic significance.

Especially in Germany, Austria, the USA and Canada rock salt is still produced in salt mines by mining or by leaching ( caverns). His breakdown in the Salzkammergut is already occupied for the time of the Celts. The largest rock salt mine in Germany is located at the city of Heilbronn. The degraded chambers taken together are over 400 km long.