12. Non-Potash Salts: Borates, Na-Sulphates, Na-Carbonate, Lithium Salts, Gypsum, Halite and Zolites

The mineral name colemanite is named after one of the early miners in the Death Valley region, Mr. William T. Coleman. Ulexite was named for the German chemist Georg Ludwig Ulex (1811–1883) who first discovered it.

In the first decades of the twentieth century the mining of Korabogazgol (Bay) raw materials for the Russian chemical industry was based on natural processes. Year-round the upper layers of water in the bay contained sodium chloride NaCl, magnesium chloride MgCl₂, and sodium sulfate Na₂SO₄. Every year, in late November, when the water temperatures dropped to 5.5–6 °C, the water became saturated with sodium sulfate, and mirabilite (Na₂SO₄·10H₂O) precipitated as colorless crystals on the bay bottom that were then transported by wind and wave action to the shorezone, especially during winter storms. In mid-March when the bay waters were heated to over 6 °C, the mirabilite on the bay floor began to redissolve. By July–August the entire precipitated mirabilite crop out in the bay had re-dissolved. The period from November through March was a period of “harvesting” mirabilite on the bay shores. In summer with its arid climate the remaining strandzone salt converted to thenardite Na₂SO₄ that was gathered at the end of each summer.

Ancient Egyptians are famous for their perfection of the art of mummification. A key ingredient in the process was natrun, which is composed of halite + trona + sodium sulphate (Edwards et al. 2007). The ancients knew its preservative properties rivalled those of halite and, as it also absorbs water readily, it is an excellent desiccant/ preservative of organic material. Natrun is found in large quantities in the beds of several Egyptian playa lakes (e.g. Wadi Natrun and El Kab, as well as Behiera in the nearby Libyan desert) and has been mined and traded from these localities for thousands of years. Writings as old as the reign of Rameses III (1198–1166 B.C.) refer to these deposits. The preservative qualities must have been immediately apparent to the ancient Egyptians from its effects on any wild life, which had died in these lakes. There is some evidence that the Egyptians artificially precipitated natrun by isolating shallow basins of lake waters for faster evaporation, as is still done in parts of the depression today. For purification and preservation, natrun was preferred over halite because it chemically attacks and destroys grease and fat and so is a superior drying agent (as is sodium borate). It is found not only in tombs and in pits, along with other discarded embalming materials, but also forms nodules and residues in the mummies themselves.

There is some debate over the method in which the natrun was used for mummification by the ancient Egyptians. Some argue it was used in a way similar to the contemporary method for “salting” fish. Dry natrun would be sprinkled over the body, perhaps with sawdust, or spread with linen cloths. Others with a more prosaic bent, believe the body was immersed in vats containing a natrun solution. Such a wet method would have been odiferous and accelerated putrefaction, thus counterproductive to the preservation of the body, although it makes for good Hollywood images. A dry body is also more readily bandaged as well as being more amenable to the attachment of amulets and other jewelry. Although mummification has supernatural trappings in popular culture and ancient religions, its basis is rooted in simple chemistry and processes as mundane as salting fish.

Mummification also occurs naturally in halite and trona is not necessary, although it improves preservation. In 1593 AD and again in 1616 AD several tombs encased in salt were exposed by natural salt weathering and collapse in the Hazel Mountains. When the coffins were opened by the local people of Hallein and Hallstatt, there was astonishment that the bodies inside had very well preserved soft tissues. It was the result of the hyperarid encasement in a Neolithic salt mine, but frightened religious locals insisted of prompt reburial with additional efforts to create effective seals. There was a similar popular response in 1734 AD when the salt preserved body of a man wearing mountain clothing (possibly a miner) was discovered. Fearful locals insisted on immediate reburial with no further study or observations on the remains (Aufderheide 2011). First in the winter of 1993 and later in 2004, in the modern Chehr Abad Salt Mine, near Hamzehloo, Zanjan Province of Iran, at total five salt-preserved male bodies were found in a collapsed tunnel of a former salt mine, which was active around 400 BC. The first discovery in the winter of 1993 was a salt encased bearded head and some artifacts, the later discovery, beginning in November 2004, was of the remaining bodies. It is likely all five men died in earthquake induced collapses in the salt mine (Pollard et al. 2008). Encasement in the hyperarid atmosphere of the collapsed salt mine tunnel led to mummification of the bodies.

Calcium sulphate has several forms, ie, calcium sulphate dihydrate (CaSO₄·2H₂O; commercially known as gypsum), calcium sulphate anhydrous (CaSO₄; anhydrite), calcium sulphate hemihydrate (CaSO₄·1/2H₂O), present in two different structures, α-hemihydrate and β-hemihydrate (commercial name of β-form: stucco or plaster of Paris).

Alabaster is a form of gypsum that is massive, fine-grained, granular and compact; the name is related to a place in ancient Egypt called Alabaston, where this mineral was quarried for sculpturing.

In the context of past seawater chemistries it is important to note that this discussion of brine origin concerns interpretation of proportions of ions present in porous non-evaporite sediment hosts. It is totally separate to interpretations of past seawater chemistries based on analyses of inclusions held in primary chevron halite crystals sampled from a impermeable bedded salt mass. In this latter case the ionic proportions of the ambient seawater concentrate are unequivocally preserved.

The human body contains approximately 5 mg of iodine, which functions only in the iodine-containing thyroid hormones. In 1990, the United Nations and WHO estimated that about one billion people are at risk for iodine deficiency disorders (IDD), 211 million with goiter (enlargement of the thyroid gland), 5.1 million with severe cognitive and neuromotor deficiencies (cretinism), and many more with less severe neuropsychological defects.

Nitre (sometimes called saltpetre) is a naturally occurring nitrate. The name saltpetre comes from medieval Latin “sal petrae” meaning “stone salt”. The saltpetre terminology can be confusing as there are types of saltpetre, namely, (1) Ordinary saltpetre, or potassium nitrate (KNO₃) and generally referred to as ‘saltpetre’ without any prefix – it was the active gunpowder component that in Medieval times was derived from dung heaps and other decomposing organic material; (2) Chilean saltpetre or “cubic nitre” or “soda nitre” or “nitratine” or sodium nitrate (NaNO₃), this is the focus of our discussion as it is the predominant nitrate salt in the Atacama Desert; (3) Lime saltpetre or wall saltpetre or calcium nitrate [Ca(NO₃)₂] or Norgessalpetre (Norwegian saltpetre) or kalksalpetre – a rare efflorescent salt in natural state.

Dead–burned magnesite (or refractory magnesia) refers to the granular product produced by firing magnesite, magnesium hydroxide, or other materials reducible to magnesia at temperatures in excess of 1,450 °C.

Calcined magnesia is the result of 800–1,000 °C heat being applied, frequently in a rotary kiln, to magnesite or other materials reducible by heat to magnesia. It is heated to such a degree that less than 10 % ignition loss remains and the product displays absorptive capacity or activity. Fused magnesia is produced by heating high grade magnesite to a molten state for up to 6 h in electric arc furnaces to temperatures approximately 3,000 °C. The resultant product, at 96–98 % MgO, has a favorable high density of 3.50 g/cc and relatively high chemical stability, strength, and resistance to abrasion.