Chessy copper mines, Chessy-les-Mines, Villefranche, Rhône, Auvergne-Rhône-Alpes, France
|Latitude & Longitude (WGS84):||45° 53' 45'' North , 4° 36' 46'' East|
|Latitude & Longitude (decimal):||45.89583,4.61278|
|Köppen climate type:||Cfb : Temperate oceanic climate|
|Name(s) in local language(s):||Anciennes mines de cuivre de Chessy|
|Other/historical region names associated with this locality:||Rhône-Alpes|
The ore deposit of Chessy-les-Mines was mined for copper in the Middle Ages until 1875. It's a "stockwerk" mineralization with barite, galena, sphalerite and chalcopyrite hosted in altered soda-dacitic lavas near the devonian Brévenne rift. This orebody was covered by Triassic sediments (clay and sandstone) which were mineralized in turn by hydrothermal fluids during their deposit. Then, primary sulphides were oxidized (during Eocene?) allowing the formation of secondary minerals of lead, zinc and especially copper (azurite, cuprite, malachite, agardite, chrysocolla ...). It is these secondary minerals that have build the celebrity of the Chessy mines, thanks to superb specimens of azurite (called here "chessylite") displayed in many collections today. This reputation has been built from 1811 when the miners opened the famous "Blue Mine" which contained many vugs of azurite. At the time of operation, engineers distinguished four different parts in the deposit:
The "yellow Mine": native ore (chalcopyrite, pyrite) in speckles or nodules in the dacites
The "black Mine": reduced ore (tenorite, native copper) in black nodules in the altered dacites (contact dacites / Triassic)
The "red Mine": oxidized ore (cuprite, limonite) released into the red clay of the Lower Triassic
The "blue Mine": highly oxidized ore (azurite, cuprite, malachite and smithonite) in clays and sandstones of Middle and Upper Triassic.
Today, the mine is closed but the dumps were bought by the Geological Club of l'Arbresle who conducts regular searches.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded from this region.
Mineral ListMineral list contains entries from the region specified including sub-localities
115 valid minerals. 2 (TL) - type locality of valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
541 - 1000 Ma
|Neoproterozoic mixed volcanic, volcaniclastic and sedimentary rocks|
Age: Neoproterozoic (541 - 1000 Ma)
Reference: Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d. 
Localities in this Region
- Chessy copper mines