Yellow Mn-Rich Tourmaline From The Canary Mining Area, Zambia

Laurs, Brendan M.; Simmons, William B.; Rossman, George R.; Fritz, Eric A.; Koivula, John I.; Anckar, Björn; Falster, Alexander U.

doi:10.5741/gems.43.4.314

Cited by 10 publications

(9 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The broad and moderately intense bands in the NIR region at ~9000 and ~14000 cm -1 , which are caused by spin-allowed transitions in Fe 2+ (Mattson and Rossman, 1987) do not contribute to the colour of the samples. The band assignments for the OGR overgrowth agree with its yellow-orange colouration due to Mn 2+ and Mn 2+ -Ti 4+ IVCT as colour-causing agents (Rossman and Mattson, 1986;Laurs et al, 2007;Pezzotta and Laurs, 2011). Considering the comparable total MnO contents of all the dark-coloured overgrowths (about 4.5 wt%), and that OGZ, OGY and OGR belong to the same crystal fragment and therefore grew at the same time, the absence of Mn 3+ d-d transitions in the OGR spectra suggests a strong preferential incorporation of Mn 2+ ions in the antilogous overgrowth, even in the presence of Mn 3+ in the crystallisation environment.…”

Section: Comparison Of the Dark Overgrowthssupporting

confidence: 54%

Dark-coloured Mn-rich overgrowths in an elbaitic tourmaline crystal from the Rosina pegmatite, San Piero in Campo, Elba Island, Italy: witness of late-stage opening of the geochemical system

Altieri

Pezzotta²,

Skogby

et al. 2022

MinMag

View full text Add to dashboard Cite

Multicoloured tourmalines from Elba Island quite frequently display dark-coloured terminations due to the incorporation of Fe, but also occasionally Mn, formed during the latest-stages of crystallisation in cavities. However, the mechanisms that led to the availability of these elements in the late-stage residual fluids are not yet completely clear. For this purpose, we studied a representative tourmaline crystal found naturally disrupted in two fragments within a wide miarolitic cavity in the Rosina pegmatite (San Piero in Campo, Elba Island, Italy), and characterised by late-stage dark-coloured overgrowths. Microstructural and paragenetic observations, as well as chemical and spectroscopic analyses (electron microprobe and optical absorption spectroscopy), provide evidence that the formation of the observed dark-coloured Mn-rich overgrowths is the https://doi.org/10.1180/mgm.2022.125 Published online by Cambridge University Press result of a pocket rupture. This event allowed chemical alteration of the cavity-coating spessartine garnet by highly-reactive late-stage cavity fluids through leaching processes, with the subsequent release of Mn to the residual fluids. We argue that the two fragments were originally a single crystal, which underwent a natural breakage followed by the simultaneous growth of Mn-rich dark terminations at both breakage surfaces. This supports the pocket rupture event, responsible for both the shattering of the tourmaline crystal and the chemical variation of the cavity-fluids through the availability of Mn, which was incorporated by tourmaline crystals. Additionally, a comparison of the dark overgrowths formed at the analogous and the antilogous poles, can provide additional information on tourmaline crystallisation process at the two different poles. The antilogous pole is characterised by a higher affinity for Ca, F and Ti, and a selective uptake of Mn 2+ even in the presence of considerable amount of Mn 3+ in the system. This uneven uptake of Mn ions caused the yellow-orange colouration of the antilogous overgrowth (Mn 2+ dependent) instead of the purplereddish colour displayed by the analogous overgrowths (Mn 3+ dependent).

show abstract

Section: Comparison Of the Dark Overgrowthssupporting

confidence: 54%

Dark-coloured Mn-rich overgrowths in an elbaitic tourmaline crystal from the Rosina pegmatite, San Piero in Campo, Elba Island, Italy: witness of late-stage opening of the geochemical system

Altieri

Pezzotta²,

Skogby

et al. 2022

MinMag

View full text Add to dashboard Cite

show abstract

“…The green elbaite samples contained more iron (up to 4.88 wt.% FeO) than the pink elbaite (maximum 0.21 wt.%), which always contained more manganese than iron (see green samples 1a, 2b, 9, 15, and 16 and pink samples 1b, 2a, 6, 8, 12, 17, and 18 in table 2). Orange and yellow elbaite (sample 7) had high manganese content (6.47 and 6.57 wt.% MnO, respectively), similar to the Mn-rich tourmaline from Zambia (Laurs et al, 2007). However, high amounts of manganese were also seen in colorless (sample 5a), grayish blue (sample 5b), and gray (sample 14) tourmaline.…”

Section: Discussionmentioning

confidence: 84%

Gem News International

2005

Gems & Gemology

View full text Add to dashboard Cite

Canadian subscribers should add GST. Discounts are available for group subscriptions, GIA alumni, and current GIA students. To purchase print subscriptions, visit store.gia.edu or contact Customer Service. For institutional rates, contact Customer Service. Database Coverage G&G is abstracted in Thomson Reuters products (Current Contents: Physical, Chemical & Earth Sciences and Science Citation Index-Expanded, including the Web of Knowledge) and other databases. For a complete list of sources abstracting G&G, go to gia.edu/gems-gemology, and click on "Publication Information." Manuscript Submissions Gems & Gemology, a peer-reviewed journal, welcomes the submission of articles on all aspects of the field. Please see the Author Guidelines at gia.edu/gemsgemology or contact the Managing Editor. Letters on articles published in G&G are also welcome. Please note that Field Reports, Lab Notes, Gem News International, Micro-World, and Charts are not peerreviewed sections but do undergo technical and editorial review.

show abstract

“…The final, lowest energy spin-allowed transition, has not been previously assigned, likely due to low intensity and/or obstruction by other features in the near-infrared . We note that when yellow “Canary” tourmalines with high Mn-content are oxidized to a deep red color it shows a prominent band at ∼1100 nm (∼9000 cm –1 ) which has previously been assigned to Fe(II) . In our tourmaline sample, which contains a very small amount of iron, the relatively intense transition at 1040 nm may be attributable to multiple transitions, which often overlap (Figure ).…”

Section: Resultsmentioning

confidence: 99%

The Nature of the Mn(III) Color Centers in Elbaite Tourmalines

2020

Self Cite

View full text Add to dashboard Cite

The characteristic red color of many natural tourmalines is due to the presence of Mn(III) cations substituting for aluminum and lithium. These sites originate as Mn(II) and are oxidized by natural γ-irradiation over geologic time as they sit in the Earth’s crust. Presented here is a thorough analysis of the spin-allowed and spin-forbidden transitions which give rise to the color of these gemstones. Ligand field analysis, supplemented by time-dependent density functional theory, was used to correct the historical assignments of the symmetry-allowed transitions in the polarized UV–visible absorption spectrum. Heat-induced reduction of the oxidized manganese sites provided a probe of the relationship between the spin-allowed and spin-forbidden bands. Notably, the intensity of the spin-forbidden transition was highly dependent on the neighboring ions in the Y-site. Simulations and modeling showed that increased intensity was observed only when two Mn(III) ions occupied adjacent substitutions in the Y-site via a proposed exchange-coupling mechanism.

show abstract

Yellow Mn-Rich Tourmaline From The Canary Mining Area, Zambia

Cited by 10 publications

References 14 publications

Dark-coloured Mn-rich overgrowths in an elbaitic tourmaline crystal from the Rosina pegmatite, San Piero in Campo, Elba Island, Italy: witness of late-stage opening of the geochemical system

Dark-coloured Mn-rich overgrowths in an elbaitic tourmaline crystal from the Rosina pegmatite, San Piero in Campo, Elba Island, Italy: witness of late-stage opening of the geochemical system

Gem News International

The Nature of the Mn(III) Color Centers in Elbaite Tourmalines

Contact Info

Product

Resources

About