Rock salt
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Rock salt

Origin of Sicilian deposits

One of nature's many marvels occurred six million years ago. The Mediterranean Sea was isolated from the Atlantic and the only parts of Sicily which were emerged were the Peloritani, Nebrodi, Sicani and Madonie mountain ranges, the Palermo and Trapani mountains and the Ibleo plateau. The area surrounded by these mountain chains was a vast briny lagoon in which the sea and rainwater that entered was less than that removed by the evaporation caused by the combined action of the sun and wind.

This led to a continuous increase in the concentration of salts until precipitation occurred: that is to say, the salts dissolved in the sea water started to sediment, layer upon layer. The first to precipitate were the less soluble salts, the carbonates and sulphates. Crystals of chlorides and sodium, magnesium and potassium sulphates have been deposited above this bed of limestone and gypsums, which formed the thick, compact lenses of alkaline salt deposits, including rock salt.

Inclusione di kainite in salgemmaIl SalgemmaGiacimento di salgemma

Particular mention must be made of the Petralia Soprana deposit, which is one of the richest deposits in Europe: it is an enormous lens of rock salt contained in the heart of the mountain rising up to 1,100 metres above sea level. The rock salt covers an area of 2 km▓ and a thickness of up to 400 m, with a sodium chloride content of up to 99.9 %. The exceptional purity of the salt and the location outside the area where the other Sicilian deposits are found, makes one think that the Petralia deposit had a secondary origin, that is to say, that they were pre-existing salt deposits which the geological events of the island dissolved, shifted and re-crystallised outside the area of its first formation.
This means that nature did by itself what man must do with sea salt; remove the gypsum and limestone detritus deposited with the salt. Petralia salt therefore naturally has a very special quality which no other salt may copy, not even with processing and manipulation which, in any case, would adversely affect the wholesomeness.

Rock salt

It takes the form of crystals, granular or fibrous aggregates, in crusts and as stalactites. Rock salt is used for the production of Sodium Chloride (NaCl), which is commonly referred to merely as salt. The crystalline salt is also known as 'Halite', the salt diamond, from the Greek αλς = salt e λιθος = rock.

Cristalli di salgemmaHaliteCristalli di salgemma

Rock salt, which is extracted from underground deposits, is a mineral found mainly in the form of extensive, thick layers; these layers are found within the rocks of all the geological ages and their thicknesses vary from a few tens of centimetres to hundreds of metres. The rocks which surround them are often clayey and they are therefore impermeable to water, thereby favouring conservation of the mineral, which would otherwise be diluted by underground waters.

Italkali extracts the rock salt from the underground deposits by means of continuous mining machines or by means of explosives. The continuous mining machine is fitted with a cutting head that crumbles the salt from the rock wall and a system which transfers it mechanically onto trucks with stainless steel boxes. Explosives are used for the production of industrial salt and road salt. The mineral obtained in this way is loaded on trucks by means of radio-controlled shovels and transferred for crushing and screening.

Useful information:

Even though all salt originates from the sea, it is still necessary to distinguish, from a quality point of view, the sea salt, produced in the salt pans by evaporation of the sea water, from rock salt, which has been deposited by the sea during geological events over millions of years and held underground, from vacuum salt obtained by re-crystallisation of a saturated brine. The different production processes can give rise to significant differences in quality.

Sea salt may, at the very most, only become as good as rock salt if it has been produced with the care and attention that the refining process requires and without which the product is not very satisfactory, not merely for food purposes but also for many industrial uses,. The raw sea salt is chemically cleaned and reduced to sodium chloride by an industrial refining process; the minerals and the essential trace elements are considered to be impurities and as such are eliminated. The sodium chloride, which is isolated and unnatural in this manner, no longer has anything natural about it, with none of the wholesomeness of genuine salt which, on the contrary, includes all the natural elements (84 minerals); the same ones which constitute our body. Consequently, as is often mistakenly believed, sea salt is certainly not better than rock salt, which, due to its higher quality, is always more costly.

Rock salt has a quality level linked to the origin of every deposit, which has its own quality standard. This quality depends on the quantity and quality of the components other than sodium chloride present in the mineral, which differs for each deposit, and, to a lesser extent, at each extraction site. And for obvious reasons, rock salt, which originates from an uncontaminated sea five million years ago, will never contain the impurities of the raw sea salt, which is affected by the malign pollution which threatens all our seas.

Vacuum salt obtained by the forced re-crystallisation of saturated brines reaches the maximum NaCl content (almost 100%). It is a relatively costly product as its production requires a large use of energy and it was therefore started specifically for chemical industry purposes. Since the consistency of the quality level is high it also has many industrial uses.

Measurement parameters
The fundamental parameters for the quality of salt are:
- NaCl content
- colour (white)
- grain size
- humidity

Each parameter is more or less important, depending on the specific needs of the various industrial uses or markets.
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