Esterellite

Esterellite (or Estérellite) is a porphyritic variety of quartz-bearing microdiorite, containing phenocrysts of quartz, zoned andesine, and hornblende only found in the southern part of the Esterel massif, between Agay and Saint-Raphael, France.

[1] It is a bluish-grey rock, sometimes greenish, dotted with white plagioclase feldspar and amphibiole crystals, forming a thick laccolithic complex near Le Drammont.

Today, it is mainly used to make riprap, such as blocks for the dykes of the ports of Saint-Raphaël and Fréjus, railway ballast and road gravel.

Esterellite is a porphyritic rock, completely crystalline, containing large phenocrysts (plagioclases, quartz, ferromagnesians), which are very visible to the naked eye, and a matrix of very small microcrystals.

[4][5] The overall composition of this rock places it among the slightly alkaline andesites and dacites of the subalkaline igneous magma series, typical of subduction zones.

[6] While the bedrock of the Esterel dates back to the formation of the Hercynian chain (pre-Carboniferous), almost all the volcanic outcrops appeared 250 million years ago at the end of the Palaeozoic era (Permian).

[10][23] Using 40Ar/39Ar dating, Féraud (1995) estimated the age of samples of esterellites from Le Dramont at 32.7 ± 0.9 Ma and concluded that they were produced during a brief and unique event affecting the outer and inner Alpine domains between the Mediterranean and the Saint Raphael area.

[27] The quartz-bearing microdiorite of Alghero (Cala Bona 40°32′41.91″N 8°19′16.11″E / 40.5449750°N 8.3211417°E / 40.5449750; 8.3211417) shows close petrographic and chemical analogies to the esterellites of the Estérel Massif.

[56][48] In the centuries that followed, it was used sparingly for decorative purposes in its production area of Fréjus, Vénasque, Cannes and Antibes, where it can be found in the form of columns and colonnettes, as well as pavements and wall coverings.

[57] There are also limited examples of reuse of antique columns in the Romanesque chapel of Saint-Nicolas in Die and in the colonnade of the cloister of the fortified Lérins Abbey ont the Saint-Honorat island in the bay of Cannes.

[67] In the 1890s, local records show that paving stones were exported to modern-day Argentina, Bulgaria (Ruse), Romania (Brăila, Galați), Russia and Turkey.

The esterellite of the Grands Caous quarry is mainly used for the production of ripraps, such as blocks for the dykes of the ports of Saint-Raphaël and Fréjus, railway ballast and road gravel.

[74][75] During World War II, the esterellite quarries were requisitioned by the Organisation Todt to supply materials for the construction of the Mediterranean Wall, along with some of the employees.

The Allies landed on 15 August 1944 on Camel Green, code name of the vast pebble beach at Le Dramont, formed by the cobbles left over from sixty years of quarrying.