“You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled underfoot." MAT5:13 (NIV)
Technically a salt is any ionic compund resulting from a neutralisation reaction but in day to day use, salt (also called common salt) refers to sodium chloride, a compound near ubiquitous on Earth and involved in the metabolism of almost all species.
Its metabolic role leads to salt being a key dietary requirement for many species and to many of those having a strong evolved taste preference for it - and thus salt has been a key condiment and trade good for most of human history. This is reinforced by salt's role as a drying and preserving agent which for much of human history has been one of very few methods for storing food (notably the sort of salted meat and fish found in iron rations, but also brine1-pickled vegetables and the like). Mineral supplements based around salt are vital for anything that sweats a lot - humans can usually deal with this by seasoning their food but herbivorous livestock will often need crude supplements to remain healthy. This used to be blocks of impure salt, but in the modern era often consists of purpose built licks with added vitamins and a scientific mix of minerals (but still mostly salt) … and even then, people who sweat around livestock will often find themselves being licked.
Besides food based uses, salt also has limited medical applications (mostly applied to wounds as an antiseptic and caking agent) and is used in a variety of industrial processes including dyeing and the glazing of ceramics. Salt can also be used to lower the melting point of water for de-icing work.
Salt has also been used historically in ritual purifications, spinkling salt on places or things as a blessing. In some cultures eating or receiving salt from someone places you under obligation to them (or, alternatively, under their protection) and is an important part of hospitality and/or vassalage rituals. In many traditions a line of salt can provide at least a temporary barrier against the supernatural.
In small quantities salt is vital to life … in large ones it is often a poison. Anything used to fresh water will be unable to drink (or live in) salt water, a diet too rich in salt can lead to blood pressure problems and, in extremis, salt ploughed into cropland can make it unusable for decades. Even without direct intent, a buildup of salt caused by poor agricultural practice has been implicated in the demise of several civilisations.
Salt is generally either mined from naturally occuring deposits (for example as rock salt) or collected by the evaporation of sea water. The produce of either operation can potentially be traded over very long distances and has historically been used as a form of commodity money. Historically it is worth noting that very few natural sources of salt consist of pure sodium chloride - in many cases a given deposit will have specific impurities with a noticable taste or chemical property, and pre-modern sources often specify the geographic source for salt for a specific purpose (since prior to the invention of analytical chemistry there was no easy way of telling the various compounds in any specific "salt" apart).
Game and Story Use
- As all trade goods, this is potential treasure.
- Also a really annoying cargo in areas where there is the potential for rain to get into it.
- For reference, traditional trade salt was shipped in pressed blocks (and still is in some parts of the world), transport as a powder tends to be a more recent phenomenon.
- Putting salt in the mouth of a voodoo zombie would traditionally de-animate it.
- If you allow salt to be used as a barrier, best have rules ready.
- The purifying power of salt is used in some traditions to contain, or even drain power from magic items - usually by storing them in a jar of salt.
- For anything with a moist body and a hydrostatic skeleton - like most molluscs - a dose of salt can be extremely harmful… salting slugs is a favourite past time amongst many young boys.