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Lo straordinario incremento di nuovi minerali della tormalina negli ultimi tre anni F ERDINANDO B OSI Dipartimento di Scienze della Terra, Sapienza Università.

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Presentation on theme: "Lo straordinario incremento di nuovi minerali della tormalina negli ultimi tre anni F ERDINANDO B OSI Dipartimento di Scienze della Terra, Sapienza Università."— Presentation transcript:

1 Lo straordinario incremento di nuovi minerali della tormalina negli ultimi tre anni F ERDINANDO B OSI Dipartimento di Scienze della Terra, Sapienza Università di Roma

2 Tourmalines are borosilicates represented by the general formula: XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W [9] X = Na, K, Ca, vacancy; [6] Y = Al, Cr, V, Fe, Mg, Mn, Li etc. ; [6] Z = Al, Cr, V, Fe, Mg; [4] T = Si, Al, B; [3] B = B; [3] W(O1) = OH, F, O; [3] V(O3) = OH, O. Tourmalines occur in a wide variety of sedimentary, igneous, and metamorphic rocks.

3 The best-known species probably are: Dravite NaMg 3 Al 6 (Si 6 O 18 )(BO 3 ) 3 (OH) 3 (OH) Schorl NaFe 3 Al 6 (Si 6 O 18 )(BO 3 ) 3 (OH) 3 (OH) Elbaite Na(Al 1.5 Li 1.5 )Al 6 (Si 6 O 18 )(BO 3 ) 3 (OH) 3 (OH)

4 T OURMALINE IS INTERESTING … – as a MINERAL – as a GEMSTONE – as a PETROLOGICAL INDICATOR – as a MATERIAL for technological applications

5 as a gemstone Tourmaline was “discovered” as a gemstone. In fact, the term tourmaline seems to be derived from the Sinhalese word turmali, which was used to refer to mixed- colored stones of unknown type by gem dealers in Ceylon (now Sri Lanka).

6 “M OTHER N ATURE ’ S RAINBOW ” Gem tourmaline is famous for its extensive range of colors, even within individual crystals: from colorless, through red, pink, yellow, orange, green, blue, and violet, to brown and black. as a gemstone

7 Tourmaline gem varieties are often known on color basis Rubellite (rose, dark pink, to red) as a gemstone

8 Verdelite (green to yellow-green) as a gemstone

9 Indicolite (blue to blue-green) as a gemstone

10 Achroite (colorless) as a gemstone

11 Canary tourmaline (yellow) as a gemstone

12 Chrome tourmaline (vivid green) as a gemstone

13 Paraíba-type (“neon” blue-to-green) is one of the highest-priced colored gemstones (values comparable to those of some diamonds, Pezzotta and Laurs 2011) as a gemstone

14 Cat’s eye and moor’s head tourmalines as a gemstone

15 As tourmalines are sensitive to physicochemical changes in their growth environment, they may be optically zoned. as a gemstone

16 Cut stones are often mounted into jewelry Pendant consisting of two Cu-bearing tourmalines (10.95 ct pink and 6.95 ct yellow) set in 18 k gold with diamonds as a gemstone

17 T OURMALINE STRUCTURE is one of the most complex as well as the most elegant of all crystal structures of rock-forming minerals as a mineral

18 The cyclosilicate structure is formed by rings of six TO 4 tetrahedra, which point in the same direction. Thus, the structure results both noncentrosymmetric and polar: thus, tourmaline is both piezoelectric and pyroelectric The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W as a mineral T-site

19 The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W Tourmaline supergroup can be classified into primary groups based on the dominant occupancy of the X site: vacant, alkali and calcic groups. This grouping makes sense because X-site occupancy usually reflects the paragenesis of the rock in which these tourmalines crystallize as a mineral X-site

20 The most extensive compositional variation occurs at the Y site. The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W Y-site is able to incorporate cations of different sizes and charges, including vacancies. as a mineral Y-site

21 The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W Boron makes tourmaline one of the most important boron- bearing minerals (reservoir of B) in the Earth’s crust. as a mineral B-site

22 Structural islands The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W as a mineral “X+Y+B+T”

23 ZO 6 octahedra link thestructural islands The tourmaline structure XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W The 3-D framework is given by ZO 6 as a mineral Z-site

24 The tourmaline structure Projected onto (0001) as a mineral

25 The tourmaline structure The 3-D framework of ZO 6 explains the tourmaline hardness (7-7½ Mohs) and lack of cleavage, making tourmaline a resistant mineral in clastic sediments. as a mineral

26 Tourmaline structure can accommodate a large range of chemically different elements: XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W [9] X = Na, Ca, Vac. >> K, Pb, Ag [6] Y = Al, Cr, V, Fe 3+, Fe 2+, Mg, Mn 3+, Mn 2+, Li >> Ti, Zn, Cu, Ni, Co, Vac., etc. [6] Z = Al, Cr, V, Fe 3+ > Mg, Fe 2+ [4] T = Si >> Al, B, Be [3] B = B [3] W(O1) = OH, F, O [3] V(O3) = OH, O B UT ITS CRYSTAL CHEMISTRY IS CONTROLLED BY STRUCTURAL CONSTRAINTS as a mineral

27 The 3-D framework of ZO 6 must be able to accommodate the structural islands as a mineral

28 Spatial relationships and reciprocal constraints of ZO 6 and YO 6 : the islands made of 3 Y are surrounded by continuous Z skeleton as a mineral

29 As YO 6 is larger than ZO 6, there is mismatch between these two non-equivalent distorted octahedra Structural constraints on chemical variability as a mineral

30 So far… as a mineral Long-range constraints 254 data from SREF

31 L ONG - RANGE DIMENSIONAL CONSTRAINTS Order-disorder reaction Y Al 3+ + Z Mg 2+ → Y Mg 2+ + Z Al 3+ applies to the tourmaline to reduce the misfit between and. By the incorporation of smaller cations (R 3+ ) into Y and larger cations (R 2+ ) into Z, decreases and increases as a mineral

32 T OURMALINE CLASSIFICATION The general formula: XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W [9] X = Na, K, Ca, vacancy; [6] Y = Al, Cr, V, Fe, Mg, Mn, Li etc. ; [6] Z = Al, Cr, V, Fe, Mg; [4] T = Si, Al, B; [3] B = B; [3] W(O1) = OH, F, O; [3] V(O3) = OH, O. The dominance of these ions at one or more sites of the structure gives rise to a range of distinct mineral species

33 Tourmaline is, in fact, not a single mineral but a supergroup currently consisting in 27 species approved by IMA-CNMNC

34 IMA-ACCEPTED TOURMALINE SPECIES From Henry et al. (2011) 1 – Dravite 2 – Schorl 3 – Elbaite 4 – Fluor-dravite 5 – Fluor-schorl 6 – Povondraite 7 – Rossmanite 8 – Fluor-buergerite 9 – Olenite 10 – Uvite 11 – Fluor-uvite 12 – Feruvite 13 – Fluor-liddicoatite 14 – Foitite 15 – Magnesio-foitite 16 – Chromo-alumino-povondraite 17 – Chromium-dravite 18 – Oxy-schorl (Bačik et al., IMA 2011-011) 19 – Tsillaisite (Bosi et al., IMA 2011-047) 20 – Fluor-elbaite (Bosi et al., IMA 2011-071) 21 – Oxy-chromium-dravite (Bosi et al., IMA 2011-097) 22 – Oxy-vanadium-dravite (Bosi et al., IMA 2012 11-E) 23 – Oxy-dravite (Bosi et al., IMA 2012-004a) 24 – Darrellhenryite (Novák et al., IMA 2012-026) 25 – Vandio-oxy-chromium-dravite (Bosi et al., IMA 2012-034) 26 – Fluor-tsilaisite (Bosi et al., IMA 2012-044) 27 – Vanadio-oxy-dravite (Bosi et al., IMA 2012-074) The last 3 years have seen an amazing increase in tourmaline species: 17 + 10 = 27

35 DraviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-draviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-draviteNa Y (MgAl 2 ) Z (MgAl 5 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) SchorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-schorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-schorlNa Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) ElbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-elbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) DarrellhenryiteNa Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) TsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-tsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Rossmanite  Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Foitite  Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Magnesio-foitite  Y (Mg 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Flour-liddicoatiteCa Y (Li 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) OleniteNa Y (Al 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (OH) Fluor-buergeriteNa Y (Fe 3+ 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (F) FeruviteCa Y (Fe 2+ 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) UviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-uviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Chromium-draviteNa Y (Mg 3 ) Z (Cr 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) PovondraiteNa Y (Fe 3 ) Z (Mg 2 Fe 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Chromo-alumino-povondraiteNa Y (Cr 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-chromium-draviteNa Y (Cr 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-vanadium-draviteNa Y (V 3 ) Z (Mg 2 V 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-chromium-draviteNa Y (V 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-draviteNa Y (V 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O)

36 DraviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-draviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-draviteNa Y (MgAl 2 ) Z (MgAl 5 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) SchorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-schorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-schorlNa Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) ElbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-elbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) DarrellhenryiteNa Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) TsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-tsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Rossmanite  Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Foitite  Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Magnesio-foitite  Y (Mg 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Flour-liddicoatiteCa Y (Li 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) OleniteNa Y (Al 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (OH) Fluor-buergeriteNa Y (Fe 3+ 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (F) FeruviteCa Y (Fe 2+ 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) UviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-uviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Chromium-draviteNa Y (Mg 3 ) Z (Cr 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) PovondraiteNa Y (Fe 3 ) Z (Mg 2 Fe 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Chromo-alumino-povondraiteNa Y (Cr 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-chromium-draviteNa Y (Cr 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-vanadium-draviteNa Y (V 3 ) Z (Mg 2 V 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-chromium-draviteNa Y (V 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-draviteNa Y (V 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O)

37 DraviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-draviteNa Y (Mg 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-draviteNa Y (MgAl 2 ) Z (MgAl 5 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) SchorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-schorlNa Y (Fe 3 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) Oxy-schorlNa Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (O) ElbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (OH) Fluor-elbaiteNa Y (Li 1.5 Al 1.5 ) Z (Al 6 ) (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 W (F) DarrellhenryiteNa Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) TsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-tsilaisiteNa Y (Mn 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Rossmanite  Y (LiAl 2 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Foitite  Y (Fe 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Magnesio-foitite  Y (Mg 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Flour-liddicoatiteCa Y (Li 2 Al) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) OleniteNa Y (Al 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (OH) Fluor-buergeriteNa Y (Fe 3+ 3 ) Z (Al 6 ) (Si 6 O 18 )(BO 3 ) 3 (O) 3 W (F) FeruviteCa Y (Fe 2+ 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) UviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) Fluor-uviteCa Y (Mg 3 ) Z (MgAl 5 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (F) Chromium-draviteNa Y (Mg 3 ) Z (Cr 6 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (OH) PovondraiteNa Y (Fe 3 ) Z (Mg 2 Fe 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Chromo-alumino-povondraiteNa Y (Cr 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-chromium-draviteNa Y (Cr 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Oxy-vanadium-draviteNa Y (V 3 ) Z (Mg 2 V 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-chromium-draviteNa Y (V 3 ) Z (Mg 2 Cr 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-draviteNa Y (V 3 ) Z (Mg 2 Al 4 ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O)

38 Nomenclature Tourmaline classification (Henry et al. 2011)

39 Tourmaline classification of Henry et al. (2011, 2013) XY 3 Z 6 (T 6 O 18 )(BO 3 ) 3 V 3 W “For the purposes of classification of tourmaline species, actual tourmaline structural information of the Y- and Z-site occupancy is an overriding consideration for the definition of a tourmaline species” Henry et al. (2013). Empirical (real) structural formula has to be used in naming the tourmaline Hence, accurate site allocation of cations and anions is needed !

40 Empirical structural formula of Clark et al. (2011): X Na Y (Mg 2+ 1.4 Al 3+ 0.6 Fe 2+ ) Z (Al 3+ 5.4 Mg 2+ 0.6 ) T (Si 6 O 18 ) B (BO 3 ) 3 V (OH) 3 W [F 0.7 (OH) 0.3 ] Fluor-dravite, end-member formula Na Y (Mg 3 ) Z (Al 6 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 (F)

41 x < 0.2 (for example, x = 0.1) Y (Fe 2+ 1.4 Mg 1.5 Al 0.1 ) Z (Mg 0.1 Al 5.9 ) Structural formula: Na Y (Fe 2+ 1.4 Mg 1.6-x Al x ) Z (Mg x Al 6-x ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 F

42 Structural formula: Na Y (Fe 2+ 1.4 Mg 1.6-x Al x ) Z (Mg x Al 6-x ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 F x > 0.2 (for example, x = 0.3) Y (Fe 2+ 1.4 Mg 1.3 Al 0.3 ) Z (Mg 0.3 Al 5.7 )

43 Nomenclature x < 0.2, fluor-dravite x > 0.2, fluor-schorl For the same bulk chemistry, the name changes as a function of the degree of order/disorder over Y and Z Structural formula: Na Y (Fe 2+ 1.4 Mg 1.6-x Al x ) Z (Mg x Al 6-x ) (Si 6 O 18 )(BO 3 ) 3 (OH) 3 F

44 Oxy-vanadium-dravite X (Na) Y (V) 3 Z (V 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O) Oxy-chromium-dravite X (Na) Y (Cr) 3 Z (Cr 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O) Vanadio-oxy-chromium-dravite X (Na) Y (V) 3 Z (Cr 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O) O XY - TOURMALINES Vanadio-oxy-dravite X (Na) Y (V) 3 Z (Al 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O) Oxy-dravite X (Na) Y (Al) 3 Z (Al 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O) Chromo-alumino-povondraite X (Na) Y (Cr) 3 Z (Al 4 Mg 2 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O)

45 Oxy-chromium-dravite Oxy-vanadium-dravite Vanadio-oxy-chromium-dravite Vanadio-oxy-dravite Chromo-alumino-povondraite O XY - TOURMALINES

46 The 5 new species of Cr-V-oxy-tourmalines occur in the Pereval marble quarry, near the town of Sludyanka (51°37′N 103°38′E), Irkutsk region, Southern Lake Baikal, Siberia, Russia The Sludyanka complex comprise sedimentary-metamorphic rocks consisting of diverse gneisses, carbonate, and carbonate-silicate rocks and mafic schists Probably, Cr-V-oxy-tourmalines were formed in the prograde stage of metamorphism (i.e., granulite facies)

47 Ternary diagram for V-Cr-Al oxy-tourmaline Na Y R 3+ 3 Z (R 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O “Intermediate" end-members

48 What are their compositional fields in the diagram V-Cr-Al? Cr tot = 5.0 and Al tot = 2.0 Cr tot = 3.0 and Al tot = 4.0 Cr tot = 1.5 and Al tot = 5.5 Example, chromo-alumino-povondraite: it is between oxy-chromium-dravite and oxy-dravite join. Z Cr 2 ↔ Z Al 2 Y Cr 1.5 ↔ Y Al 1.5

49 Ternary diagram for V-Cr-Al oxy-tourmaline Na Y R 3+ 3 Z (R 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O

50 Site preference: Y V > Y Cr > Y Al Z Al > Z Cr > Z V ?

51 Ternary diagram for V-Cr-Al oxy-tourmaline Na Y R 3+ 3 Z (R 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O Site preference: Y V > Y Cr > Y Al Z Al > Z Cr > Z V Confirmed by a systematic study (work in progress)

52 Nomenclature (Henry et al. 2013) “In the absence of specific structural information on the Y- and Z-site occupancies, a procedure is recommended for allocating cations to Z and Y... Initially assign all Al 3+ (in excess of that assigned to T) to the Z site. Next, successively assign Mg 2+ (up to 2 apfu), V 3+, Cr 3+, and Fe 3+. If there is an excess of trivalent cations on Z, it goes into Y”. Chemical analysis, sample PR1973 (Na ~1 apfu, Mg ~2, V 3+ ~2.2, Cr ~3.8, Al ~1, Si ~6, B = 3, OH ~3) Recommended formula according to Henry et al. (2013): Na Y (Cr 3 ) Z (Al 1 Mg 2 V 2.2 Cr 0.8 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Empirical formula according to the structural information: Na Y (Cr 0.8 V 2.2 ) Z (Al 1 Mg 2 Cr 3 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O)

53 Nomenclature (Henry et al. 2013) “In the absence of specific structural information on the Y- and Z-site occupancies, a procedure is recommended for allocating cations to Z and Y... Initially assign all Al 3+ (in excess of that assigned to T) to the Z site. Next, successively assign Mg 2+ (up to 2 apfu), V 3+, Cr 3+, and Fe 3+. If there is an excess of trivalent cations on Z, it goes into Y”. Chemical analysis, sample PR1973 (Na ~1 apfu, Mg ~2, V 3+ ~2.2, Cr ~3.8, Al ~1, Si ~6, B = 3, OH ~3) Recommended formula according to Henry et al. (2013): Na Y (Cr 3 ) Z (Al 1 Mg 2 V 2.2 Cr 0.8 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Empirical formula according to the structural information: Na Y (Cr 0.8 V 2.2 ) Z (Al 1 Mg 2 Cr 3 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O)

54 Nomenclature (Henry et al. 2013) “In the absence of specific structural information on the Y- and Z-site occupancies, a procedure is recommended for allocating cations to Z and Y... Initially assign all Al 3+ (in excess of that assigned to T) to the Z site. Next, successively assign Mg 2+ (up to 2 apfu), V 3+, Cr 3+, and Fe 3+. If there is an excess of trivalent cations on Z, it goes into Y”. Chemical analysis, sample PR1973 (Na ~1 apfu, Mg ~2, V 3+ ~2.2, Cr ~3.8, Al ~1, Si ~6, B = 3, OH ~3) Recommended formula according to Henry et al. (2013): Na Y (Cr 3 ) Z (Al 1 Mg 2 V 2.2 Cr 0.8 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Empirical formula according to the structural information: Na Y (Cr 0.8 V 2.2 ) Z (Al 1 Mg 2 Cr 3 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 W (O) Vanadio-oxy-chromium-dravite X (Na) Y (V) 3 Z (Mg 2 Cr 4 ) T (Si 6 O 18 )(BO 3 ) 3 V (OH) 3 W (O)

55 Ternary diagram for V-Cr-Al oxy-tourmaline Na Y R 3+ 3 Z (R 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O Boundaries within the diagram?

56 Ternary diagram for V-Cr-Al oxy-tourmaline in accord with the recommendations of Henry et al. (2013), except for V 3+ and Cr 3+ 1) Y (Al 1 Cr 1 V 1 ) Z (Al 4 Mg 2 ) 2) Y (Cr 1.5 V 1.5 ) Z (Al 4 Mg 2 ) 3) Y (Cr 1.5 V 1.5 ) Z (Cr 2 Al 2 Mg 2 ) 4) Y (V 3 ) Z (Cr 2 Al 2 Mg 2 ) 5) Y (V 3 ) Z (V 1.33 Cr 1.33 Al 1.33 Mg 2 )

57 Ternary diagram for V-Cr-Al oxy-tourmaline in accord with the recommendations of Henry et al. (2013), except for V 3+ and Cr 3+

58 Na Y (Cr 1.4 V 1.6 ) Z (Mg 2 Cr 1.9 Al 2.1 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O Cr tot = 3.3 > Al tot = 2.1 > V tot = 1.6 Vanadio-oxy-dravite Ternary diagram for V-Cr-Al oxy-tourmaline in accord with the recommendations of Henry et al. (2013), except for V 3+ and Cr 3+

59

60 Coming soon… Special Collection on Spinels in American Mineralogist Spinels Renaissance: The past, present and future of those ubiquitous materials A special collection, focused on diverse topics, related to the structure, properties and applications of natural and synthetic spinels and spinelloids on bulk and nanoscale. The section aims at the revival of the interest in the spinel materials at present and particularly on the promising future of the non-oxygen containing and nanosized structures. We hope to bring together experimental and theoretical research studies from mineralogists, geologists, chemists, materials scientists, physicists and crystallographers. Papers will undergo normal peer review, conducted by special collection associate editors Kristina Lilova, Kaimin Shih and Ferdinando Bosi.


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