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The remarkable cerium occurrence in the Bastnas ore field was the first deposit ever mined for cerium, and one of the few localities in the world for cerium minerals. For a long time it was the only known locality for cerite. It is also the type locality for allanite-(Ce), bastnasite-(Ce), cerite- (Ce), lanthanite-(Ce), tornebohmite-(Ce) and linnaeite, as well as for the elements cerium and lanthanum.
INTRODUCTION
The Riddarhyttan ore field is situated in the county of Vastmanland, south-central Sweden, about 70 kilometers northwest of Vasteras and 180 km west-northwest of Stockholm. Specimens from Bastnas, e.g. of cerite, are rather widespread in public and private collections in Europe, and the collection of the Naturhistoriska Riksmuseet (Swedish Museum of Natural History) in Stockholm contains a large suite of Bastnas specimens, including the type specimen of tornebohmite.
For many years the authors and other collectors have dug in the dumps at Bastnas in the hope of finding the classic rare-earths-containing species once mined here. In the mid-1980's a rich zone of rare-earth minerals was discovered at a depth between 0.5 and 1 meter in the dumps, about 30 meters from the Sankt Goransgruvan mine. The zone contained many cerium minerals, as well as some species new for Bastnas and for Sweden (bismutite, brochantite and wroewolfeite). Presently, 37 species are known from the locality.
HISTORY
The Riddarhyttan ore field is part of the vast mining and foundry area named Bergslagen, in south-central Sweden, where tens of thousands of different mines have been worked for nearly a thousand years. Iron, copper, cobalt and cerium have been intermittently mined in the Riddarhyttan ore field for about six centuries. The ore field is divided into some 15 smaller fields, with approximately 300 large and small mines. Iron ore mining began in the mid- 14th century, and prospecting for copper ore began during the 16th century, on the initiative of the Swedish king Gustavus I (Gustav Vasa). The last active iron and copper mine, Backegruvan, was closed by its owner, Fagerstabruk, in 1978.
Unless otherwise indicated, the following data concerning the mine's history are compiled from Carlborg (1923). Mining at Bastnas is recorded with certainty from the mid-14th century, making this district one of the oldest in Sweden. Though the mine was...