for Trapani, where we picked up Professore Stefano Lugli, Charlotte’s PhD student from “many years ago”, who is also an expert on evaporite rocks (rocks that form from precipitates due to the evaporation of seawater, like salt!). After recharging ourselves with espressi and gelati at the Trapani train station, we continued our drive to the Trapani Salt Works, the oldest salt works in Europe whch have origins as far back as 800 B.C.We first visited a small salt museum which houses an original windmill from the 14th century that used to grind the salt (yes, grind. The salt that results from evaporation ponds is very coarse, often more than 1cm in size). Our guide was the owner, who got really passionate and excited about her topic! We knew this because the rate at which she spoke increased exponentially, to the point that our two Italian speakers, Tina and Sanjoy, lost track of the explanations..oopps! Luckily Stefano was there to help us translate what our guide was saying. We also discovered that salt produced entirely with the labor of people is of better quality than “mass produced salt”, since mass-production includes processing, such as cleaning and filtering of the salt that remove the important bromide, iodine and other healthy elements. Salt is also found within rocks (which are mined). Such salt coming from mountains has “matured”. It is thus a lot older than “fresh marine salt”, and has lost most of its fluid inclusion, which is where the bromide and iodine are located. This is why iodine is often added to salt coming from rock, as opposed to salt from evaporative processes.
The salt making process occurs in 4 stages. During the first stage, water is collected into a big pond and brought in by the high tide. The second pond, which is slightly higher in elevation, is fed by an Archimedes screw! Today, the screw is driven by electric pumps, but it is amazing that they still use the screw to drive water to higher elevation!
From stage 2, the water continues on to ponds in stages 3 and 4 that are shallow to maximize evaporation. Carbonates (like limestone) and gypsum (found in wallboards) precipitate first, and mostly in ponds 2 and 3. Below the gypsum crusts, we found thriving cyanobacterial mats (cyanobacteria are bacteria that produce oxygen), visible in thin layers of green and red below the gypsum. Below that, a thick black mat was found, with a light gray aragonitic layers (aragonite is a limestone of different crystal structure). This black layer released substantial hydrogen sulfide, or “rotten egg smell”, indicating that sulfur-reducing bacteria were present, and creating the hydrogen sulfide as part of their metabolic activiy. Those bacteria are strictly anaerobes, and thus indicate that the black layer is in an anoxic setting (devoid of oxygen). In the last pond, halite (salt) precipitates. The pond has the appearance of a coarse snow field! The resulting salt is thus very coarse and the cubic structure of the crystal is very apparent!
Following the excitements of the Salt Works, we left for Segesta, where a beautifully imposing Greek temple, built in the late 5th century B.C, blooms on a hillside. We spent some time in the ruins of the town of Segesta on the opposite hill before soaking into the grandeur of the greek temple. What majesty! However, it is an interesting fact that the temple was never finished: its columns are not fluted, and apparently, it was never roofed.
The drive home was uneventful and the evening was dedicated to working on our reports, blogging, eating pizza and drinking wine… but mainly working on our reports ;)
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