How the salt is mined
It is white, odourless and tastes salty. The distinguishable properties of salt are pretty unspectacular, yet this apparently inconspicuous matter has always been a subject of great scientific interest.
As early as in the 4th century, Hilary of Poitiers, a Doctor of the Catholic Church, took a visionary opinion. He reasoned "that salt contained both the element of water and of fire and that the two had thus become one".
In principle, he was right, even if his elemental classification was not to be confirmed by modern science. The constituent parts of common salt, the positively charged sodium ions (Na+) and the negatively charged chloride ions (Cl-) bond in a dramatically efficient way. The particles form crystals, but are at the same time extremely soluble in water. It is a property that has been exploited in salt mining for centuries. Whereas the Celts and the Romans worked the mountain using only a pick-axe, a more sophisticated method was to be developed as early as in the Middle Ages, with the invention of "solution mining".
Water is injected into the Haselgebirge rock through adits, the salt dissolves and the highly concentrated salt brine is extracted from the mine. The system is maintained, even though today the more efficient borehole probe technique is used wherever the salt content is sufficiently concentrated in the rock. Two pipes are installed in a drilled well that is several hundred metres deep. One pipe is used to inject water at high pressure, which forces the saturated brine out through the other pipe.