The Silverworks mines at Eiker

Ever since Kongsberg Sølvverk and Kongsberg were founded in 1624, there has been a close connection between Bergstaden and the neighboring village of Eiker – among other things, the very first silver finds were smelted in Kongens smelhytte in Vestfossen. In the latter half of the 18th century, the Sølvverk employed 400 people, and it had several mines and shards in Eiker – including the “Christianus VI and Dronning Sophie Magdalena mine” in Skarraenga outside Vestfossen, the Kjennerudvannsgruvene in Lurdalen and the Schwabegruva on Grasåsen.

The most significant activity, however, was that which was started around 1770 in the outlying areas under the farms Skarra and Kolberg, right on the border with Svene parish in Numedal. This became known as the "Schara Ertzdyb Grube" or simply "Skarragruvene".

At this time, the Silver Works started up in several areas that were quite far from the main fields in Saggrenda. This was because the operation of these mines was becoming less profitable, and therefore richer deposits were sought. Optimism was great, and at the Skarra mines, more than 20 sharp points were taken up, two horizontal adits were driven in, totaling around 700 meters in length, and a crushing plant was built, which was powered by hydroelectric power from Dørja. The operation provided work for 50-60 people - at most, around 100 miners were active there.

In the long run, the results did not meet expectations, and in 1898 the Skarra mines were closed down after 30 years of operation. This was part of the winding up of Kongsberg Sølvverk, where all operations ceased in 1805. It was not until ten years later that mining operations resumed, but operations were never as extensive as they had been at the end of the 18th century.