Gypsum is a mineral (calcium sulphate dihydrate CaSO4*2H2O) that together with other salts, as sodium chloride (the common salt that is used in the kitchen), normally it’s dissolved in the sea water. It is part of so-called “evaporite” minerals, that are formed by the deposition from an aqueous solution full of salts, subjected an intensive evaporations; with the water evaporation, the solutions become ever more full of salts, till these pass from liquid to solid state, falling into the bottom.
- If pure, it’s is colorless;
- Has a vitreous or silky brightness;
- It isn’t too hard, so it let be easily scratched by a nail;
- It is perfectly split apart in parallel foil;
- It can be dissolved in the water (in 1 liter of water at 20° C can be dissolved about 2.5 grams of gypsum).
Gypsum is present in nature in different shapes: crystals of various dimension (from the micron to some metre) or detrital particles that came from the crystal disintegration. The gypsum rocks that emerge from big areas of the Sicily, belong to the “Chalky-Sulphurous Series”, represent a big geological and cultural heritage that must be valorized. They represent a peculiar element of Sicilian geology, so have been studied for long time for them geological and mining aspects and for the incredible diversity of the shape -superficial and subterranean- that the mountainous relief take from in the areas where they emerge. The rocks of the Chalky-Sulphurous Series are strictly connected to the Sicily history because they have been places of many mines and quarry for the extraction of the gypsum, Sulphur and salt.
In this space we can discover the extraordinary history of the Sicilian chalky rocks’ origin.
As every mineral, the gypsum presents a crystalline structure and some physics and chemical features. Frequently, crystals appear like “dovetail” .