The Rosia Montana deposit is one of the oldest mining sites in the world, with a history stretching back some 2000 years.
There have been four principal mining periods:
- Roman conquest period (106 - end of the 3rd century)
- Austrian-Hungarian Empire conquest (from the end of the 17th century until 1918)
- The period between the two World Wars (1918 - 1939)
- Modern Age (1939 up to present).
The Romans mined out gold rich veins using galleries which followed the vein direction. During Austro-Hungarian Empire times mining operations were developed in Carnic, Cetate, Jig and Orlea along the more highly mineralized veins using underground methods.
Between the two World Wars many concession contracts were awarded to local people which permitted the mining of gold for a defined period of time, resulting in many of the rich gold veins being mined out. The ore was transported by foot to water powered stamp batteries from which the gold contained in the veins was collected. Gold was then extracted using amalgom (mercury) which was burnt off to recover the bullion (gold and silver).
More recently, due to modern mining methods and the lower grade disseminated style mineralization within the bulk of the rock, mining operations were developed underground using stope and pillar bulk mining methods and as the average gold content of the remaining rock decreased further, ore was recovered using open pit methods with gold recovered in a flotation plant situated at Gura Rosiei. The resulting concentrate was then trucked to Baia de Aries, 28km away, and gold and silver were recovered using conventional cyanide leaching techniques.