Geology
The Evje og Hornnes municipality is situated at the south-western margin of the Baltic Shield, the exposed section of the East European craton. Rocks in the area are dominated by different types of precambrian gneis and a large metagabbro body stretching into the neighboring Iveland municipality.
During the final stages of Sveconorwegian (0,9-1,1 Ga) orogeny, a large pluton of granitic/monzonitic composition was emplaced in the northern part of the municipality, and is assumed to have a relationship with the thousands of pegmatite veins in the Evje-Iveland area.
Earlier during the Sveconorwegian orogeny mafic rocks (gabbro-diorite) were emplaced. Most of the gabbro has been affected by the Sveconorwegian orogeny and became a metagabbro (amfibolite) with only minor remnants of the original gabbro. The Flåt Nickel Mine is situated at the north-western margin in a diorite intrusion post-dating the gabbro.
The pegmatites of the Evje-Iveland area have become worldwide known for a large number of rare and often beautifully crystallized minerals.
The pegmatites were initially mined for quartz, used in the melter at Fennefoss to extract the nickel from the ore from the Flåt Nickel Mine. Later large quantities of feldspar were mined for use in the ceramic industry, both in Norway and abroad. Also mica (muscovite), beryl, rare earth elements—containing minerals, scandium ore, and minor quantities of uranium ore were mined.
After 1983, almost all mines were abandoned, and nowadays only minor quantities of "tannspat" or dentalspat are mined in a 1-2 mines. This is microcline or plagioclase feldspar of very high purity, and used to make porcelain teeth-fillings or dentures. The tannspat is exported to Germany, Liechtenstein, Austria, and sometimes Japan.
A number of the mines is still open to mineral collectors who hope to find some of the beautiful crystals the area is known for.
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