Kongsberg Silver Mines
The silver mines of Kongsberg, in Buskerud county in Norway, constitute the largest mining field in Norway, with over 80 different mines. It was the largest pre-industrial working place in Norway, with over 4,000 workers at its peak in the 1770s and supplied over 10% of the gross national product of the Danish–Norwegian union during its 335-year-long history: over 450,000 man-years were expended in the production.
Geology of Estonia
Oil shale in Estonia remains a major part of the economy and throughout the 1950s, '60s, '70s, '80s and early '90s, geologists extensively prospected oil shale resources, with peak production in 1980. Phosphorite mining was also an important activity in Estonia through the 1980s, prompting the so-called Phosphorite War in 1987 when the Estonian public opposed the expansion of mining efforts, and the implicit threat of additional Russian miners being sent to the region. The major phosphorite mine at Maardu closed in 1991 due to its environmental impact. 
Estonia has 165,000 mires (including 20,000 peat bogs), each with an area of one hectare or greater. About 1500 are commercially important and most have thicknesses of three to seven meters, with a maximum of 16.7 meters in the Haanja Heights.
Lake chalk is sometimes used to neutralize high acidity and for art material. Estonia also has iron ore in the crystalline basement, pyrite and glauconite and, as well as lead and zinc sulfide ore. Granite rock near Tallinn is often extracted for road work.