Diatomite was a leading export commodity in 2002, and ferrosilicon production and geothermal power were Iceland's major mineral industries. Diatomite production, from Lake Myvatn, was 28,000 tons in 2001, and the Ministry of Environment issued a permit for dredging in a new area of the lake, as government studies determined that additional mining would not damage the environmentally sensitive lake. Iceland also produced hydraulic cement, nitrogen, pumice, salt, scoria, sand (basaltic, calcareous, and shell), sand and gravel, and crushed stone (basaltic and rhyolite); these minerals were used by local industries. Among Iceland's other mineral resources, spar and sulfur deposits, once mined, were no longer worked extensively; peat was common, but little used; and sulfur and lignite were being processed experimentally, the former with the use of subterranean steam. The country's aluminum plant and ferrosilicon plant relied on imported raw materials and inexpensive hydroelectric and geothermal energy.