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Mn-bearing purplish...
Mn-bearing purplish-red tourmaline from the Anjanabonoina pegmatite, Madagascar
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- Bosi, Ferdinando (author)
- Sapienza Università di Roma, Italy
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- Celata, Beatrice (author)
- Sapienza Università di Roma, Italy
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- Skogby, Henrik (author)
- Naturhistoriska riksmuseet,Enheten för geovetenskap
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- Hålenius, Ulf (author)
- Naturhistoriska riksmuseet,Enheten för geovetenskap
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- Tempesta, Gioacchino (author)
- University of Bari "Aldo Moro", Italy
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- Ciriotti, Marco (author)
- University of Turin, Italy
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- Bittarello, Erica (author)
- Univerity of Turin, Italy
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- Marengo, Alessandra (author)
- Univerity of Turin, Italy
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(creator_code:org_t)
- 2021-03-01
- 2021
- English.
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In: Mineralogical magazine. - : Mineralogical Society. - 0026-461X .- 1471-8022. ; 85:2, s. 242-253
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https://nrm.diva-por... (primary) (Raw object)
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https://www.cambridg...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Subject headings
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- A gem-quality purplish-red tourmaline sample of alleged liddicoatitic composition from the Anjanabonoina pegmatite, Madagascar, hasbeen fully characterised using a multi-analytical approach to define its crystal-chemical identity. Single-crystal X-ray diffraction, chem-ical and spectroscopic analysis resulted in the formula: X(Na0.41□0.35Ca0.24)Σ1.00Y(Al1.81Li1.00Fe3+0.04Mn3+0.02Mn2+0.12Ti0.004)Σ3.00ZAl6[T(Si5.60B0.40)Σ6.00O18](BO3)3(OH)3W[(OH)0.50F0.13O0.37]Σ1.00, which corresponds to the tourmaline species elbaite having the typical space group R3m and relatively small unit-cell dimensions, a= 15.7935(4) Å, c= 7.0860(2) Å and V= 7.0860(2) Å3.Optical absorption spectroscopy showed that the purplish-red colour is caused by minor amounts of Mn3+(Mn2O3= 0.20 wt.%).Thermal treatment in air up to 750°C strongly intensified the colour of the sample due to the oxidation of all Mn2+ to Mn3+ (Mn2O3 up to 1.21 wt.%). Based on infrared and Raman data, a crystal-chemical model regarding the electrostatic interaction betweenthe X cation and W anion, and involving the Y cations as well, is proposed to explain the absence or rarity of the mineral species ‘liddicoatite’.
Subject headings
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)
Keyword
- The changing Earth
- Den föränderliga jorden
Publication and Content Type
- ref (subject category)
- art (subject category)
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