| Reference Type | Journal (article/letter/editorial) |
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| Title | Manganvesuvianite and tweddillite, two new Mn3+-silicate minerals from the Kalahari manganese fields, South Africa |
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| Journal | Mineralogical Magazine |
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| Authors | Armbruster, T. | Author |
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| Gnos, E. | Author |
| Dixon, R. | Author |
| Gutzmer, J. | Author |
| Hejny, C. | Author |
| Döbelin, N. | Author |
| Medenbach, O. | Author |
| Year | 2002 (February) | Volume | 66 |
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| Issue | 1 |
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| Publisher | Mineralogical Society |
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| DOI | doi:10.1180/0026461026610018Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 243330 | Long-form Identifier | mindat:1:5:243330:5 |
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| GUID | 0 |
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| Full Reference | Armbruster, T., Gnos, E., Dixon, R., Gutzmer, J., Hejny, C., Döbelin, N., Medenbach, O. (2002) Manganvesuvianite and tweddillite, two new Mn3+-silicate minerals from the Kalahari manganese fields, South Africa. Mineralogical Magazine, 66 (1) 137-150 doi:10.1180/0026461026610018 |
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| Plain Text | Armbruster, T., Gnos, E., Dixon, R., Gutzmer, J., Hejny, C., Döbelin, N., Medenbach, O. (2002) Manganvesuvianite and tweddillite, two new Mn3+-silicate minerals from the Kalahari manganese fields, South Africa. Mineralogical Magazine, 66 (1) 137-150 doi:10.1180/0026461026610018 |
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| Abstract/Notes | AbstractThe new minerals manganvesuviante and tweddillite, both formed by hydrothermal alteration of primary manganese ores, are described from the Kalahari manganese fields (Republic of South Africa). In addition, single-crystal X-ray structure refinements of both new minerals are presented.Manganvesuvianite is a tetragonal vesuvianite mineral with the simplified formula Ca19Mn3+(Al,Mn3+,Fe3+)10(Mg,Mn2+)2Si18O69(OH)9, characterized by Mn3+ occupying the five-coordinated position (square pyramid). The crystals simple prismatic forms: {100}, {110} terminated by {101} and exhibit deep maroon red colour. With polarized light the crystals are strongly pleochroic, yellowish parallel to E and dark red to lilac parallel to O.Tweddillite is an epidote-group mineral (space group P21/m, a = 8.932(5), b = 5.698(4), c = 10.310(5) Å, β = 114.56(4), V = 477.3(8) Å3) with the simplified formula CaSr(Mn3+,Fe3+)2Al[Si3O12](OH), closely related to strontiopiemontite. The difference between strontiopiemontite and tweddillite is the concentration of octahedral Mn3+. Strontiopiemontite has Mn3+ mainly on the M3 site whereas tweddillite has Mn3+ with minor Fe3+ on M3 and M1. Tweddillite forms aggregates of very thin dark red {001} blades characterized by striking pleochroism. The crystals appear dark red parallel to b and orange-yellow parallel to a. Perpendicular to (001) the blades appear magenta to red. |
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