archive materials. An oil shale research institute (now a department within Tallinn University of Technology) was founded at Kohtla-Järve in 1958. Preliminary research into oil shale-based chemical production began the same year, exploring the potential for the use of oil shale in bitumen, synthetic construction materials, detergents, synthetic leathers, synthetic fibres, plastics, paints, soaps, glues, and pesticides. Between 1959 and 1985, of mineral wool were produced from oil shale coke, a solid residue of oil shale. In 1968, a branch of the Skochinsky Institute of Mining was established in Kohtla-Järve, and in 1984 the scientific-technical journal Oil Shale was founded in Estonia. Developments in independent Estonia In the 1990s, after Estonia regained independence, the country underwent a restructuring of the economy, causing the collapse of a large part of the heavy industry sector. This collapse led to a decrease in the consumption of electricity and thus a decrease in the need for the oil shale that was mined to produce it. Electricity and shale oil export to former Soviet markets largely ceased. Due to a decrease in demand, the Tammiku and Sompa mines closed in 1999 and those at Kohtla and Ahtme closed in 2001. In 1995, state-owned shale oil producers in Kohtla-Järve and Kiviõli were merged into the single company named RAS Kiviter. In 1997, Kiviter was privatized and a year later it declared insolvency. Its factories in Kohtla-Järve and Kiviõli were sold separately and new oil producers – Viru Keemia Grupp and Kiviõli Keemiatööstus – emerged. In 1995, the Government of Estonia started negotiations with American company NRG Energy to create a joint venture on the basis of the Narva Power Stations, the largest consumer of oil shale in Estonia. As a part of the deal, 51% of the government-owned shares in the oil shale mining company Eesti Põlevkivi was transferred to the Narva Power Stations. The proposed deal with NRG Energy met a strong public and political opposition and was cancelled after NRG Energy failed the deadline to secure financing for the project. Consequently, the Government transferred its remained shares in Eesti Põlevkivi to a state-owned company Eesti Energia, a parent company of the Narva Power Stations, and Eesti Põlevkivi became a fully owned subsidiary of Eesti Energia. Oil shale production started to increase again in the beginning of the 21st century. In 2000, the open-pit mines at Viivikonna, Sirgala and Narva were merged into the single