Grube Clara

In „Grube Clara“, located in the Rankach Valley in Oberwolfach, the industrial minerals baryte and fluorite are being mined underground. For further preparation the material is being transported to the processing plant located 13 km away from the mine.

The annual extraction of crude ore amounts to 80.000 tons of baryte and 70.000 tons of fluorite. The different kinds of Mahlspat (filling materials) being produced out of the crude ore containing baryte are being used as a basic material. in automobile industry e.g for sound absorption, fitted carpets, plastics and underbody coating. Further applications take place in the fields of deep drilling technology, radiation protection and heavyweight concrete, e.g as counterweights for tower cranes.

The majority of the mined fluorite is used in welding technology as a flux agent in welding electrodes and welding powders. In chemical industry it is a basic material to produce fluor.

The natural mineral deposits of Grube Clara consist of various veins which were formed by hydrothermical processes.

The baryte vein, known since the Middle Ages, is 600 metres long and has an average thickness of 3,4 metres. Meanwhile it has been mined up to depth of 800 metres. The fluorite vein lies parallel to the baryte vein and has an average thickness of 3 metres. The two veins are cut by a huge geological disruption and another vein called "Diagonaltrum" which is 2,5 metres thick and also contains baryte as well as fluorite. However it is workable in some small areas only.


	There are two possibilities to get to the mineral deposit by truck: the Rankach adit and the main ramp that meanwhile has reached a length of almost 5 kilometres.

	The mining areas are accessible by so-called spiral ramps and crosscuts which meet the sublevels lying one upon the other every 12 metres. All driftways are excavated by means of drilling and rock blasting. For protection they are consolidated with anchor plates and shotcrete.

The mining of the veins is performed in seven steps that are constantly being repeated:

Drilling and rock blasting from the lower level to the level located above
Loading of the blasted crude ore with special loaders
Drilling and blasting to prepare the next exploitation (from the upper to the lower level)
Loading of the crude ore with remote-controlled loaders
After having completed the mining process the hollow spaces are being refilled
Construction of a shotcrete wall
Filling up with secondary rocks and binder material

The loaders topple the crude ore over into small shafts (ore passes). Trucks are being loaded from these shafts. They transport the crude ore directly to the processing plant in Wolfach where it is tilted on different stockpiles.
In the course of the dressing process the crude ore is being broken and washed, separated according to the specific weight, if necessary ground, floatated, dried and stored in different product silos from where the final products, mainly as flours, are being packed in so-called big bags or loaded directly into silo trucks.