The Oreana tungsten deposit is unique among American tungsten deposits in that the scheelite mineralization is considered pegmatitic. Beryl, oligoclase, albite and phlogopite are associated with it; fluorite and quartz form adjacent masses. The customary garnet and epidote are virtually absent. This mineralization differs considerably from the western quartz-vein type.Two forms of scheelite deposition occur: (1), in complex pegmatite dikes that cut metadiorite; (2), in lens-like masses along an inclined contact between limestone and metadiorite.Zones of silicification and alteration lead downward from the limestone-metadiorite contact within the limestone, but contain only traces of scheelite. It is believed, however, that such zones represent channelways leading to ore deposition above and are pegmatitic in character.

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