AFRICA
Fluorite from the El Hammam Mine in Morocco
Stunning shot of a spectacular fluorite from this quarry. Outstanding quality, colorful and gemmy. Very fluorescent under ultraviolet light. Specimen beautifully finished. The brightness, habit, transparency and quality of the crystals is unsurpassed.
El Hammam Mine is a fluorite mine located about 43 km SW of Meknès. The mine is named after the mountain on which it sits: Djebel el Hammam. "El Hamman" is a frequent mis-nomer.
The mine, the only fluorite mine in Morocco, works several veins, the El Hammam vein, the Bergamou vein and the Gouaida vein. The Bergamou and Gouaida veins are oriented E-W and bear mostly purple fluorite, while the El Hammam vein is located NE-SW and bears the familiar pale green fluorite.
The deposit is characterised by unusually high REE content in fluorite and carbonates. El Hammam district is a fluorite vein field with zonality centered on a peraluminous hidden granite apex (geothermal area with centrifugal deposition and temperature decreasing towards the periphery).
The apex has developed an important contact metamorphism zone and a peraluminous monzogranite apophyse. The contact metamorphism zone is characterized by W/Sn veins with B/F minerals.
This major dislocation zone of Hercynian basement is also characterized by the presence of microgranite and dolerite veins older than the granite apex.
Fluorite veins are affected by the same subhorizontal ENE-WSW Permian compression that played a role during Sn/W mineralization. El Hamman main vein and its satellites are hosted by Middle Visean schists and limestones. Fluorite veins ettled during the ENE-WSW compression phase.
El Hamman main vein is more than 4 km long.
The main vein filling is as follows :
1) Early spathic calcite
2) Green fluorite
3) Banded fluorite/Pyrrhotite/
4) Dolomite + quartz, Leaching of green fluorite
5) Late yellow fluorite and hexagonal calcite crystals
The core of El Hamma field shows decreasing temperature brines (200-100 °C) and the circulation of hydrothermal solutions followed by more superficial fluids.
The edge of the vein field contains fluorite veins and stockwerks, of lower deposition temperature.
An internal aureole shows metric veins of green fluorite, sulfides and baryte (periphery of the veins).
An external aureole shows stockwerks and lenses of fluorite within microgranite dykes ; green and yellow fluorite is present, as well as sulfides. Almost no calcite is to be found.
Some El Hammam field veins :
- Berkamène vein : EW, fluorite without calcite, thickness increases when the vein crosses Visean limestone layers. Hydrothermal fluids : 22 %NaCl- 8 %CaCl2 T homogénéisation = 120-130 °C
- Gouaïda W vein : Analog to Berkamène vein
- Jebel Kifane : Analog to Berkamène vein
- Tlatzema vein : Analog to Berkamène vein
- Vein N° III (parallel to El Hammam main vein)
- Boulbab vein : Analog to Tirika vein
- Tirika vein : Stockwerks of fluorite within microgranites veins T homogeneisation = 110 °C
Credit: www.mindat.org/
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