ALUMINA | ILLUMINATION

In Gardanne, the GR 2013 trail passes an iconic emblem of industrial anthrogeology, the Rio Tinto processing plant.  First established in 1893, the facility refines raw bauxite ore into different grades of calcined alumina. One variety - "ultra pure alumina", is used in the manufacture of ceramic cores for high pressure sodium vapor lamps, the most prevalent form of contemporary street lighting.

In a sense, the factory manufactures illuminated nightscapes that place observers in a mesopic mode of perception. In daylight, the human eye is in a photopic state - perceiving light through color-sensitive cone receptors in the retina. In darkness, vision shifts to a scotopic mode, using rod receptors that do not perceive color. The mesopic state is in between, a twilight modality that functions in semi-darkness with reduced color perception. Evening exploration of GR 2013 trail along corridors of sodium vapor streetlight provides multiple avenues into the evocative and often dream-like quality of mesopic landscapes.

Gardanne site map

GR 2013 mesopic landscapes