Sulfur, Aragonite, Bitumen

Cozzo Disi Mine, Casteltermini, Agrigento Province, Sicily, Italy

13x10x5,5 cm. (main Sulfur crystal about 2 cm.)

This specimen is a synthesis of the dramatic geological events that occurred in the Mediterranean. It consists of a series of well-formed individual sulfur crystals with the typical yellow color and good transparency, resting on a matrix of dark brown Aragonite, caused by the widespread presence of Bitumen, which is excellently crystallized on the back. In terms of origin, association, positioning and quality of the sulfur crystals, this specimen can be considered not only highly representative but also very aesthetic.

The extraction of Sulfur in Sicily was closely tied to the extreme poverty in which Sicilians lived, where even many children, known as “Carusi“, worked in the mines under conditions akin to slavery, and below is a testimony :

a sad recent story…but what happened 5/6 millions years ago ?

The Messinian salinity crisis was a geological event during which the Mediterranean Sea went into a cycle of nearly complete desiccation (drying-up) throughout the latter part of the Messinian age of the Miocene epoch, from 6 to 5 million years ago. It ended with the Zanclean flood, when the Atlantic reclaimed the basin. During this dramatic event, selective sedimentation of dissolved salts began in order of time and chemical properties : first were Carbonatic deposit (CaCO₃), second were Chalky deposit (CaSO₄) and for last Sodium/Potassium Chloride (NaCl – KCl) deposits, all presents and well represented in Sicily. Between the two deposits of Carbonate and Gypsum, a series of anaerobic bacteria or/and the presence of hydrocarbons have fixed the Sulphur, as element, following this sequence of chemical reactions :

a)  2CaSO4 + 2CH4 (or anaerob.bact.) – -> Ca (HS)2 + CaCO3 + CO2 + 3H2O

b)  Ca (HS)2 + CO2 + H2O – – > CaCO3 + 2 H2S

c)  3H2S + CaSO4 – – > 4S + Ca (OH)2 + H2O

d)  the real consequence was : Gypsum – – > Calcite + Sulfur.

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