A 100-million-year-old geology The bright colors of the Luberon quarries originate from a geological process that began 100 million years ago when Provence was submerged under a shallow sea.%%CITE_1%% Layers of sand containing an iron-bearing clay mineral called glauconite settled on the seabed.%%CITE_1%% After tectonic movements caused the sea to recede, these green sands were exposed to a humid, tropical climate.%%CITE_1%% Weathering transformed the unstable glauconite, altering the iron into more stable forms. This process created the ochre sands, which are a mixture of about 90% silica sand and 10% pure ochre pigment.%%CITE_1%%
The specific color of the ochre depends on its chemical state. The yellow pigment, known as goethite (α-FeO(OH)), is a hydrated iron oxide. The red pigment is hematite (Fe₂O₃), which is an anhydrous iron oxide. The area contains at least 17 distinct shades, derived from these iron compounds. This palette has been used by humans for millennia; evidence of ochre use appears in French burial sites from 200,000 years ago and famously in the 17,000-year-old cave paintings at Lascaux.
The industrial ochre boom
While quarried since Roman times, the industrial-scale exploitation of Luberon's ochre began in the 1780s. A local inventor, Jean-Étienne Astier of Roussillon, developed an efficient method for separating the pigment from the sand. His process involved washing the excavated ochre sands to remove the silica, allowing the much finer pigment particles to settle in decanting basins. Once the water was drained and the pigment paste dried, it was cut into bricks, crushed, and sifted.
This innovation launched a major industry. By the late 19th century, the Vaucluse region was the world's leading producer of ochre. The industry reached its peak in 1929, when 20 factories and over 1,000 workers extracted 40,000 tonnes of pigment. The ochre was exported globally for use in paints, rubber, linoleum, and textiles. The arrival of synthetic pigments and the economic crisis of 1929 initiated a steep decline, and most quarries and factories closed by the mid-20th century. Today, only one company, the Société des Ocres de France, commercially extracts ochre in the nearby town of Gargas.