Nigerite from the Rosendal pegmatite and aplites, Kemiö island, southwestern Finland
Nigerite occurs as small hexagonal platy crystals in the Rosendal pegmatite and in associated aplitic veins on Kemiö island, southwestern Finland. This is the first reported occurrence of nigerite in the Baltic Shield. Associated minerals are quartz, hercynite or gahnite spinel, plagioclase, muscovi...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Geological Society of Finland
1977-12-01
|
| Series: | Bulletin of the Geological Society of Finland |
| Online Access: | http://www.geologinenseura.fi/bulletin/Volume49/sgs_bt_049_2_pages_151_157.pdf |
| Summary: | Nigerite occurs as small hexagonal platy crystals in the Rosendal pegmatite and in associated aplitic veins on Kemiö island, southwestern Finland. This is the first reported occurrence of nigerite in the Baltic Shield. Associated minerals are quartz, hercynite or gahnite spinel, plagioclase, muscovite, sillimanite, garnet, columbite-tantalite, chrysoberyl, tourmaline, apatite, corundum, Zn-bearing staurolite, and cassiterite. Nigerite has been formed under conditions of oversaturation of Al by desilicification of the pegmatite system. Microprobe analyses of the Rosendal nigerite were calculated by a general formula: R2+2‒2XSnXR3+4O8, with R2+ = Zn, Fe2+, Mg, Mn, and Ca, R3+ = Al, Fe3+, Nb, Si, and Ti, and x = around 0.5. The Fe/Zn ratio of the different nigerite crystals is controlled by the initial composition of the associated spinel.
|
|---|---|
| ISSN: | 0367-5211 1799-4632 |