Gypsum, which is used to produce plaster, appears here and there on the hillsides of the Haute-Provence Geopark. The Siron quarry was in operation until 1940.
The built heritage of Haute-Provence is inextricably linked to its geology. Gypsum has always been widely used in this region, due to the numerous gypsum outcrops nearby.
Formed around 220 million years ago, gypsum is a soft mineral composed of calcium sulfate di-hydrate. It played a major role in shaping the landscape of the Haute-Provence Geopark long after it had accumulated, acting as a “soap layer” (tectonic sliding surface).
Heated in a kiln, it loses some of its water and is transformed into plaster. In Thoard, of the several quarries attested in the 19th century, the Siron quarry was the best known. Here, stone was extracted with picks and pickaxes, then transported to the village’s plaster factory. Plaster was used for masonry, plastering and decoration. In Thoard, the fireplace of the former Château des Barras is one of Provence’s finest gypseries.
