Cristian Biagioni

A Milk and Ochre Paint Mixture Used 49,000 Years Ago at Sibudu, South Africa

Gas chromatography/mass spectrometry, proteomic and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) analyses of residue on a stone flake from a 49,000 year-old layer of Sibudu (South Africa) indicate a mixture of ochre and casein from milk, likely obtained by killing a lactating wild bovid. Ochre powder production and use are documented in Middle Stone Age South African sites but until now there has been no evidence of the use of milk as a binder. Our analyses show that this ochre-based mixture was neither a hafting adhesive nor a residue left after treating animal skins, but a liquid mixture consisting of a powdered pigment mixed with milk; in other words, a paint medium that could have been applied to a surface or to human skin. The significance of our finds also lies in the fact that it establishes the antiquity of the use of milk as a binder well before the introduction of domestic cattle in South Africa in the first millennium AD.

The systematics of the spinel-type minerals: An overview

Abstract Compounds with a spinel-type structure include mineral species with the general formula AB2φ4, where φ can be O2-, S2-, or Se2-. Space group symmetry is Fd3̄m, even if lower symmetries are reported owing to the off-center displacement of metal ions. In oxide spinels (φ = O2-), A and B cations can be divalent and trivalent (“2-3 spinels”) or, more rarely, tetravalent and divalent (“4-2 spinels”). From a chemical point of view, oxide spinels belong to the chemical classes of oxides, germanates, and silicates. Up to now, 24 mineral species have been approved: ahrensite, brunogeierite, chromite, cochromite, coulsonite, cuprospinel, filipstadite, franklinite, gahnite, galaxite, hercynite, jacobsite, magnesiochromite, magnesiocoulsonite, magnesioferrite, magnetite, manganochromite, qandilite, ringwoodite, spinel, trevorite, ülvospinel, vuorelainenite, and zincochromite. Sulfospinels (φ = S2-) and selenospinels (φ = Se2-) are isostructural with oxide spinels. Twenty-one different mineral species have been approved so far; of them, three are selenospinels (bornhardtite, trüstedtite, and tyrrellite), whereas 18 are sulfospinels: cadmoindite, carrollite, cuproiridsite, cuprokalininite, cuprorhodsite, daubréelite, ferrorhodsite, fletcherite, florensovite, greigite, indite, kalininite, linnaeite, malanite, polydymite, siegenite, violarite, and xingzhongite. The known mineral species with spinel-type structure are briefly reviewed, indicating for each of them the type locality, the origin of the name, and a few more miscellaneous data. This review aims at giving the state-of-the-art about the currently valid mineral species, considering the outstanding importance that these compounds cover in a wide range of scientific disciplines.

Mobilization of Tl-Hg-As-Sb-(Ag,Cu)-Pb sulfosalt melts during low-grade metamorphism in the Alpi Apuane (Tuscany, Italy)

We report the discovery of an exceptional assemblage of Tl-Hg-As-Sb-(Ag,Cu)-Pb sulfosalts showing textural evidence for their mobilization as melts in the barite–pyrite–iron oxide orebodies of the Monte Arsiccio mine (Alpi Apuane, Tuscany, Italy). The relative abundance of rare thallium sulfosalts (including three new mineral species), their peculiar textural features within the orebodies (e.g., migration along matrix grain boundaries, drop-like internal textures, low interfacial angles between sulfosalts and matrix minerals), and the overall high thallium content in pyrite from the entire mining district (to ∼900 ppm) make the barite–pyrite–iron oxide deposits of the Alpi Apuane a reference locality for studying low-temperature sulfosalt melts in low-grade metamorphic complexes (greenschist facies). Our study reveals how sulfosalt melting during low-grade regional metamorphism controls the redistribution of economically valuable and environmentally critical elements such as thallium in sulfide orebodies containing significant amounts of low-melting-point chalcophile elements.

Mercury-arsenic sulfosalts from the Apuan Alps (Tuscany, Italy). II. Arsiccioite, AgHg2TlAs2S6, a new mineral from the Monte Arsiccio mine: occurrence, crystal structure and crystal chemistry of the routhierite isotypic series

Abstract The new mineral species arsiccioite, AgHg2TlAs2S6, was discovered in the baryte-pyrite-iron oxide ore deposit exploited at the Monte Arsiccio mine, near Sant’Anna di Stazzema (Apuan Alps, Tuscany, Italy). It occurs as anhedral grains scattered in microcrystalline baryte, associated with cinnabar, laffittite, protochabournéite, pyrite, realgar, Hg-bearing sphalerite and stibnite. Arsiccioite is red, with a metallic to sub-metallic lustre. Minimum and maximum reflectance data for COM wavelengths in air are [l (nm): R (%)]: 471.1: 29.0/29.4; 548.3: 27.6/28.3; 586.6: 26.1/26.5; 652.3: 24.2/24.6. Electron microprobe analyses give (wt.%): Cu 0.78(6), Ag 8.68(21), Zn 0.47(27), Fe 0.04(1), Hg 35.36(87), Cd 0.20(5), Tl 18.79(33), As 10.77(19), Sb 4.75(10), S 18.08(21), Se 0.07(5), total 97.99(44). On the basis of SMe = 6 a.p.f.u., the chemical formula is Ag0.87(2)Cu0.13(1)Zn0.08(4)Fe0.01(1)Hg1.91(5)Cd0.02(1)Tl1.00(2) (As1.56(2)Sb0.42(1))∑1.98S6.12(6)Se0.01(1). Arsiccioite is tetragonal, I4̄2m, with a 10.1386(6), c 11.3441(5) Å, V 1166.1(2) Å3, Z = 4. The main diffraction lines of the powder diagram are [d(in Å), visually estimated intensity, hkl]: 4.195, m, 211; 3.542, m, 103; 3.025, vs, 222; 2.636, m, 114; 2.518, s, 400 and 303. The crystal structure of arsiccioite has been refined by single-crystal X-ray data to a final R1 = 0.030, on the basis of 893 observed reflections. It shows a three dimensional framework of (Hg,Ag)- centred tetrahedra (1 M1 + 2 M2), with channels parallel to [001] hosting TlS6 and (As,Sb)S3 disymmetric polyhedra. Arsiccioite is derived from its isotype routhierite M1CuM2Hg2TlAs2S6 through the double heterovalent substitution M1Cu+ + M2Hg2+ → M1Hg2+ + M2Ag+. This substitution obeys a steric constraint, with Ag+, the largest cation relative to Hg2+ and Cu+, entering the largest M2 site. The ideal crystal chemical formula of arsiccioite is M1HgM2(Hg0.5Ag0.5)2TlAs2S6. The crystal chemistry of the routhierite isotypic series is discussed. Finally, the distribution of Hg ore minerals in the Apuan Alps is reviewed.

Nomenclature tunings in the hollandite supergroup

The hollandite supergroup includes a number of manganese (IV) and titanium oxides, often referred to as tunnel oxides due to their structural features, i.e. octahedral walls, 2 × 2 octahedra wide, cross-linked to each other to build up a tunnel structure. Tunnels host mono- and divalent cations, and water molecules. Based on the nature of the tunnel cation, the generic formula of these minerals may be written as either A 2+ [M 4+ 6 M 3+ 2 ]O 16 (more rarely, A 2+ [M 4+ 7 M 2+ ]O 16 ) or A + [M 4+ 7 M 3+ ]O 16 (more rarely, A + [M 4+ 7.5 M 2+ 0.5 ]O 16 ), where A 2+ = Pb, Ba, Sr; A + = K, Na; M 4+ = Mn, Ti; M 3+ = Mn, Fe, Cr, V; M 2+ = Fe. The hollandite supergroup is divided into two groups depending on the dominant tetravalent cation in the octahedral walls: the coronadite group (M 4+ = Mn), and the priderite group (M 4+ = Ti). Two main considerations led to the preparation of this report: ( i ) M 3+ (or M 2+ ) cations, even if they share the same site as M 4+ , are essential for charge-balance, therefore each combination of dominant A 2+ (or A + ), M 4+ , and M 3+ (or M 2+ ) cations corresponds to a distinct species; ( ii ) the presence/absence of “zeolitic” water in the tunnels should not represent the discriminant between two species. Based on these guidelines, our main actions have been the following: hollandite is redefined as the Ba-Mn 3+ end-member of the coronadite group; concurrently, type hollandite is redefined as ferrihollandite, a new name to denote the Ba-Fe 3+ end-member; ankangite is discredited, as a H 2 O-free variety of mannardite; the ideal endmember formulae of all known minerals of the hollandite supergroup are defined; six potentially new mineral species in the hollandite supergroup are envisaged. This report has been approved by the IMA CNMNC.

The tobermorite supergroup: a new nomenclature

Abstract The name ‘tobermorites’ includes a number of calcium silicate hydrate (C-S-H) phases differing in their hydration state and sub-cell symmetry. Based on their basal spacing, closely related to the degree of hydration, 14, 11 and 9 Å compounds have been described. In this paper a new nomenclature scheme for these mineral species is reported. The tobermorite supergroup is defined. It is formed by the tobermorite group and the unclassified minerals plombierite, clinotobermorite and riversideite. Plombierite (‘14 Å tobermorite’) is redefined as a crystalline mineral having chemical composition Ca5Si6O16(OH)2 · 7H2O. Its type locality is Crestmore, Riverside County, California, USA. The tobermorite group consists of species having a basal spacing of ~11 Å and an orthorhombic sub-cell symmetry. Its general formula is Ca4+x(AlySi6-y)O15+2x-y · 5H2O. Its endmember compositions correspond to tobermorite Ca5Si6O17 · 5H2O (x = 1 and y = 0) and the new species kenotobermorite, Ca4Si6O15(OH)2 · 5H2O (x = 0 and y = 0). The type locality of kenotobermorite is the N’Chwaning II mine, Kalahari Manganese Field, South Africa. Within the tobermorite group, tobermorite and kenotobermorite form a complete solid solution. Al-rich samples do not warrant a new name, because Al can only achieve a maximum content of 1/6 of the tetrahedral sites (y = 1). Clinotobermorite, Ca5Si6O17 · 5H2O, is a dimorph of tobermorite having a monoclinic sub-cell symmetry. Finally, the compound with a ~9 Å basal spacing is known as riversideite. Its natural occurrence is not demonstrated unequivocally and its status should be considered as “questionable”. The chemical composition of its synthetic counterpart, obtained through partial dehydration of tobermorite, is Ca5Si6O16(OH)2. All these mineral species present an order-disorder character and several polytypes are known. This report has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification.

Omsite, (Ni,Cu)2Fe3+(OH)6[Sb(OH)6], a new member of the cualstibite group from Oms, France

Abstract Omsite (IMA 2012-025) is a new mineral from the Correc d’en Llinassos, Oms, Pyrénées-Orientales Department, France. It occurs as bright yellow to amber yellow discoidal tablets, flattened on {001}, which form rosettes typically 50-100 μm in diameter. Omsite generally crystallizes on siderite without associated supergene minerals; it occurs less commonly with glaukosphaerite. Crystals have a vitreous to resinous lustre, and are transparent to translucent. Omsite is not fluorescent in either short-wave or long-wave ultraviolet light. It has an estimated hardness of 3 on the Mohs’ scale, is brittle with an irregular fracture, and has one poor cleavage on {001}. The calculated density is 3.378 g cm-3. Crystals are uniaxial (-), with indices of refraction of ω = 1.728(3) and ε = 1.66(1), measured in white light. Pleochroism is ω = orange-yellow, ε = pale orange-yellow; ω > ε. The empirical formula [based on 12 (OH + Cl) p.f.u.] is (Ni1.0992+Cu0.6652+Mg0.107Fe0.0453+)∑1.916Fe1.0003+(Sb0.9475+As0.072Na0.029)∑1.048OH11.967Cl0.033. Omsite crystallizes in space group P3̅, with unit-cell parameters a = 5.3506(8), c = 19.5802(15) Å, V = 485.46(10) Å3 and Z = 2 determined by single crystal X-ray diffraction. The five strongest lines in the X-ray powder diffraction pattern [d in Å, (Irel), (hkl)] are as follows: 4.901, (100), (004); 4.575, (83), (011); 2.3539, (81), (114̅); 1.8079, (48), (118̅); 3.781, (34), (103). The crystal structure was solved to R1 = 0.0896 for 356 observed reflections [Fo>4σFo] and 0.1018 for all the 469 unique reflections. Omsite is a layered double hydroxide (LDH) mineral, with a topology consistent with members of the hydrotalcite supergroup and cualstibite group.

Single crystal refinement of the structure of baghdadite from Fuka (Okayama Prefecture, Japan)

the crystal structure of baghdadite, ideally Ca3zr(si2o7)o2, was refined using 1986 reflections to R = 0.034. Baghdadite is monoclinic, space group P21/a, with cell parameters a 10.432(3), b 10.163(2), c 7.356(2) Å, b 90.96(2)°. the refined crystal structure is in agreement with the structure of synthetic Ca3zrsi2o9. the structure is characterized by the presence of walls of cation polyhedra, four columns large, linked together by both direct connection as well as by disilicate groups. Baghdadite is the first phase in the cuspidine group in which the Pauling’s fourth rule is violated. riassUnto la struttura cristallina della baghdadite, formula ideale Ca3zr(si2o7)o2, è stata raffinata fino ad un indice di accordo R = 0.034, utilizzando 1986 riflessi. la baghdadite è monoclina, gruppo spaziale P21/a, con parametri di cella a 10.432(3), b 10.163(2), c 7.356(2) Å, b 90.96(2)°. la struttura raffinata è sostanzialmente identica a quella del composto sintetico Ca3zrsi2o9. È caratterizzata dalla presenza di muri di poliedri, connessi tra loro sia per condivisione di vertici sia attraverso gruppi disilicato. la baghdadite è l’unica fase del gruppo della cuspidina in cui non è rispettata la quarta regola di Pauling. KEy worDs: baghdadite; cuspidine group; crystal structure. introDUCtion Baghdadite is a quite rare calcium zirconium disilicate belonging to the cuspidine group, a series of silicates with general formula M4(si2o7)X2, where M denotes cations with various charges and ionic radii, characterized by an octahedral to roughly octahedral coordination. as described by Merlino and Perchiazzi (1985a), the crystal structure of the minerals in the cuspidine family is formed by two kinds of modules whose connection gives rise to the structures of the various phases: four columns wide ‘octahedral’ walls, extending along [001], and disilicate groups. the octahedral walls are interconnected by corner-sharing, forming the framework common to all the minerals in this family. the different ways in which the diorthosilicate groups may be connected to the octahedral walls give rise to the observed different unit cells and symmetries. another difference is obviously related to their crystal chemistry, linked to the various possible cationic distributions within the polyhedra. Baghdadite was found in melilite skarn in contact with banded diorite from the Dupezeh Mountains, Qala-Dizeh region, nE iraq, and PeriOdicO di MineralOgia established in 1930 Period. Mineral. (2010), 79, 3, 1-9 doi: 10.2451/2010PM0013 http://go.to/permin An International Journal of MINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY, ORE DEPOSITS, PETROLOGY, VOLCANOLOGY and applied topics on Environment, Archeometry and Cultural Heritage Single crystal refinement of the structure of baghdadite from Fuka (Okayama Prefecture, Japan) Cristian Biagioni*, ElEna BonaCCorsi, natalE PErChiazzi and stEfano MErlino Dipartimento di scienze della terra, Università di Pisa, Via santa Maria 53, i-56126 Pisa, italy Submitted, June 2010 Accepted, September 2010 * Corresponding author, E-mail: biagioni@dst.unipi.it biagioni:periodico 30/11/2010 13:26 Pagina 1

Lead-antimony sulfosalts from Tuscany (Italy). XVI. Carducciite, (AgSb)Pb6(As,Sb)8S20, a new Sb-rich derivative of rathite from the Pollone mine, Valdicastello Carducci: Occurrence and crystal structure

Abstract The new mineral species carducciite, (AgSb)Pb6(As,Sb)8S20, has been discovered in the baryte-pyrite- (Pb-Ag-Zn) deposit of the Pollone mine, near Valdicastello Carducci, Apuan Alps, Tuscany, Italy. It occurs as black metallic prismatic crystals, up to 0.5 mm long, associated with pyrite and sterryite. Its Vickers hardness (VHN10) is 61 kg/mm2 (range: 52-66), corresponding to a Mohs hardness of ~2½-3. In reflected light, carducciite is dark grey in colour, moderately bireflectant; internal reflections are very weak and deep red in colour. Reflectance percentages for the four COM wavelengths [Rmin, Rmax (%) (λ)] are: 35.8, 40.8 (471.1 nm), 33.7, 39.0 (548.3 nm), 32.7, 37.6 (586.6 nm) and 30.4, 35.1 (652.3 nm). Electron microprobe analysis gives (wt.% - mean of six analyses): Ag 3.55(12), Tl 0.13(3), Pb 41.90(42), Sb 17.79(19), As 12.41(14), S 22.10(17), total 97.9(6). On the basis of ∑Me = 16 a.p.f.u., the chemical formula is Ag0.96Tl0.02Pb5.91As4.84Sb4.27S20.14. The main diffraction lines, corresponding to multiple hkl indices, are (relative visual intensity): 3.689 (s), 3.416 (s), 3.125 (s), 2.989 (s), 2.894 (s), 2.753 (vs), 2.250 (s). The crystal-structure study gives a monoclinic unit cell, space group P21/c, with a 8.4909(3), b 8.0227(3), c 25.3957(9) Å , β 100.382(2)°, V 1701.63(11) Å3, Z = 2. The crystal structure has been solved and refined to a final R1 = 0.063 on the basis of 4137 observed reflections. It can be described within the framework of the sartorite homologous series, as formed by chemically twinned layers of the dufrénoysite type. The simplified idealized structural formula, based on 20 sulfur atoms, can ideally be written as (AgSb)Pb6(As,Sb)∑=8S20. Carducciite is an (Ag,Sb)-rich homeotype of dufrénoysite, stabilized by the complete coupled substitution 2 Pb2+ = Ag+ + Sb3+ on a specific site of the crystal structure. Together with barikaite, it belongs to the rathite sub-group of P21/c homeotypes of dufrénoysite, of which the crystal chemistry is discussed. The distribution of Ag, coupled with As or Sb on specific sites, appears to be the main criterion for the distinction between the three species of this sub-group.

Comparative modular analysis of two complex sulfosalt structures: sterryite, Cu(Ag,Cu)3Pb19(Sb,As)22(As–As)S56, and parasterryite, Ag4Pb20(Sb,As)24S58

The crystal structures of two very close, but distinct complex minerals of the lead sulfosalt group have been solved: sterryite, Cu(Ag,Cu)(3)Pb(19)(Sb,As)(22)(As-As)S(56), and parasterryite, Ag(4)Pb(20)(Sb,As)(24)S(58). They are analyzed and compared according to modular analysis. The fundamental building block is a complex column centred on a Pb(6)S(12) triangular prismatic core, with two additional long and short arms. The main chemical and topological differences relate to the short arm, which induces a relative a/4 shift (~2 Å along the elongation parameter) of the constitutive rod layers, as illustrated by distinct cell settings within the same space group (P2(1)/n and P2(1)/c, respectively). Selection of the shortest (i.e. strongest) (Sb,As)-S bonds permitted to enhance the polymeric organization of (Sb,As) atoms with triangular pyramidal coordination. These two quasi-homeotypic structures are expanded derivatives of owyheeite, Ag(3)Pb(10)Sb(11)S(28). The hierarchy of organization levels from zero- to three-dimensional entities is subordinated to building operators, which appear as the driving force for the construction of such complex structures. Minor cations (Ag, Cu) or the As-As pair in sterryite secure the final locking, which favours the formation of one or the other compound.