Fe23+Sn3O9,一个未定名的斜钒钛矿族的铁、锡氧化物

Fe,Sn氧化物矿产于四川雪宝顶钨锡矿床中,与之紧密共生的矿物是黑气电石,白云母,石英等,Fe-Sn氧化物呈细小的不规则颗粒嵌在锡石中,粒度大小为0.013 mm～0.052 mm之间,偶有个别大的颗粒(d=0.28 mm)淡红褐色,条痕无色,玻璃-金刚光泽,无解理,(因大小硬度无法测定),Dx=5.93 g/cm3.在偏光镜下淡黄褐色,多色性弱,明显的非均质性,按N=1+dk公式,获得N=2.11,矿物的的化学成份SnO273.70,TiO20.60,Fe 2O3 25.26,总计99.56(7个不同测点的平均值),计算出化学式为Fe 23+Sn3O9.矿物的强X射线值3.702(15,511),3.445(5,901),3.348(100,505),3.264(14,711),3.114(40,712),1.487(10,033),单斜晶系,晶胞参数a=3.375 nm,b=0.457 nm,c=2.001nm,β=93°24',V=3.080 74 nm3,Z=18.     

西藏蛇绿岩豆荚状铬铁矿中简单氧化物矿物组合及其超高压成因

最近在西藏罗布莎蛇绿岩豆荚状铬铁矿中,发现包括金刚石、柯石英和某些简单氧化物,诸如SiO2、MgO、Fe2O3、Cr2O3、Al2O3以及(Si,Ti)O2等组成的矿物群。这些矿物是非常复杂的由70~80种矿物组成的地幔矿物群的一部分。这充分证实在地幔中存在简单氧化物。高压-高温相平衡实验表明,硅酸盐矿物在下地幔条件才可分解成FeO、MgO和SiO2等简单氧化物(>670km)。因此有理由认为罗布莎简单氧化物可能来自下地幔深部。     

新矿物丁道衡矿-（Ce）：珀硅钛铈矿的同质多象体和硅钛铈矿亚族C（1）位上的钛类似矿物

丁道衡矿-(Ce):(Ce,La)4Fe2 (Ti,Fe2 ,Mg,Fe3 )2Ti2Si4O22,理想的结构化学式Ce2Ce2Fe2 Ti2Ti2Si4O22单斜晶系,α=1.34656(15)nm,b=0.57356(6)nm,c=1.10977(12)nm,β=100.636(2)°,V=0.84239(46)nm3,空间群P21/a(假C2/m),Z=2.作为硅钛铈矿(chevkinite)族矿物的新成员,它产于举世闻名的白云鄂博铁.稀土.铌矿床镁夕卡岩中,多数单晶体长0.2～1.0 cm,最大者长大于1.5 cm.共生矿物有透辉石、透闪石、钠透闪石、褐帘石-(Ce)、磁铁矿、尖晶石、烧绿石、氟金云母、氟磷灰石、石英和萤石等.矿物具有褐色条痕和半金属一金属光泽的黑色,其褐黑色碎片半透明.性脆、具有贝壳状断口、无解理和裂开.显微硬度(VHN25g)为606.0～717.4 kg/mm/12(相当于摩氏硬度约5.9).矿物实测密度4.83(7)g/cm3,计算密度值4.88(0)g/cm3.丁道衡矿-(ce)的反射色为带灰色的浅黄色,多色性为不同色调的灰色.平均反射率(λ=589nm)为11.4%～12.5%.矿物为二轴晶负光性.作过结构精测的丁道衡矿-(Ce)晶体的电子探针测值:SiO2:19.29,TiO2:18.26,A12O3:0.04,FeO:8.49,Fe2O3,:1.67,ThO2:0.16,MgO:1.32,CaO:2.17,Nb2O5:0.47,Ta2O5:0.00,La2O3:19.53,Ce2O3:28.08,Y2O3:0.00,Na1O:0.01,总量99.46%;其中Fe3 /Fe2 的比值依穆斯堡尔谱换算.根据结构精测每个单位分子式中O=22和C(1)位上Ti优先占位,计算的矿物晶体化学式为(Ce2.13,La1.49Ca0.48Th0 01)Σ4.11Fe2 (Tin0.88Fe2 0.47Mg0.41 Fe0.0)Σ2.03(Ti1.96Nb0 04)Σ2.00(Si2O7)2O3.分别用P21/a和C2/m对丁道衡矿-(Ce)的晶体结构作了精测.结果表明,丁道衡矿-(Ce)的真空间群是P20/a.换言之,它才是真正珀硅钛铈矿[perrierite-(Ce)]的同质多象体.显而易见,硅钛铈矿族矿物既可以有P21/a空间群,又可以有C2/m空间群.     

金伯利岩中新发现的两种Zr-Ti、REE-Ti氧化物矿物──上地幔含大阳离子Cr、Ti、Fe氧化物矿物研究之四

在研究沂蒙矿、蒙山矿等地幔矿物时，新发现了两种Zr－Ti、REE－Ti氧化物矿物。Zr－Ti氧化物新相6个样品点的探针成分分析（wt％）：TIO227.756～46.811，ZrO231.724～58.092，TFeo2.75～5．82，CrO31．728～4．765，Nb2O51．353～4．357，Ta2O50．155～2.814，SiO20．894～13．749，主次元素的成分变化幅度均较大，但以氧为4计算的阳离子总数均为2，因此分子式可简写为（Ti，Zr，Si，Fe）2O4或（Ti，Zr）2O4，与人工化合物ZrTiO4相似。REE－Ti氧化物矿物新相的成分也较复杂，主要元素为REE（Ce，Nd，La，Sm，Pr…）及Ti，次要元素有Nb，根据五个样点的探针分析结果，简化的分子式（Ce…）2（Ti…）3O9，与人工化合物Ce2Ti3O8.7类似，属等轴晶系。两个新矿物相均产于蒙山矿中的微裂隙和熔融交代海绵边中，呈斑点状、蠕虫状、微脉状，组成元素复杂，不同颗粒分析点成分有差异，且在同一微脉中成分也有变化，反映了这两种新矿物相是非平衡的交代一结晶产物。从矿物的产出关系和成分的特征来看，它们的形成与地幔流体交代作用有关。     

钇（Y）在铁钛氧化物中的地球化学行为地质论评2009 年钇（Y）在铁钛氧化物中的地球化学行为——以峨眉山大火成岩省为例

钛铁矿和钛磁铁矿是火成岩中最常见的副矿物,查明钇（Y）及Ti/Y值与铁钛氧化物的分离结晶/堆积作用的关系对于利用微量元素来探讨岩石成因具有重要的科学意义。峨眉山大火成岩省中的溢流玄武岩及与其具有成因联系的层状岩体均有不同含量的钛磁铁矿或钛铁矿,本文通过对其TiO2含量与FeO*(FeO*为全铁含量,FeO*=FeO+09Fe2O3)、Y与Ti/Y的相关性研究,发现与前人的实验成果并不完全一致,在TiO2含量较低时（TiO2<7%）,Y在铁钛氧化物中具有一定的相容性,而在大量铁钛氧化物存在时（TiO2>7%）,则表现为不相容性。但是岩石中存在一定量的铁钛氧化物时,其Ti/Y值则随TiO2含量的增高而增高,所以该比值不能反映源区的特征。在铁钛氧化物含量较低或基本不含时,Ti/Y值则与TiO2的含量无关,可能对源区具有指示意义。     

电子探针定量分析FeO与Fe203的新方法:峰形拟合直接测定法

用电子探针微区成分分析(EPMA)方法来测定矿物岩石的微区成分已经是当前岩矿分析的常用方法,但EPMA不能直接测定矿物中的FeO和Fe2O3.通过探讨电子探针分析中影响氧和铁峰位的一些主要因素,结合计算机蜂形拟合软件的应用,提出了峰形拟合直接测铁法测定FeO和Fe2O3质量分数的方法.本方法适用于硅酸盐矿物中Fe2+和...     

南苏鲁超高压变质带东海地区富钛榴辉岩及金红石矿的成因

苏鲁超高压变质带南部的东海地区有富Fe—Ti的钛铁矿榴辉岩和富Ti的金红石榴辉岩。富Fe—Ti榴辉岩的次要矿物主要由钛铁矿和钛磁铁矿组成，可舍少量金红石，具有很低的Si02（38．0％-42．3％）、Na20＋K20（0．48％～2．13％）和Zr、Nb、Ta、Ba、1Kb、REE含量，很高的FeO（18．24％-25．33％）、V和Co含量，并具有不同程度的LREE亏损、明显的正Eu异常；富Ti金红石榴辉岩舍有丰富的金红石和磷灰石，SiO2含量范围（38．0％-54．8％）较宽，FeO含量较低，P2O5含量较高（可达4．1％），而X-TiO2与P205含量具正相关性。相对于原始地慢岩．富Ti金红石榴辉岩具有Rb、Th、K、Nb、Pr、Nd、Eu、Ti、Lu的负异常和Ba、Sr、Zr的正异常．并具相对较高的IKEE含量，LREE富集和HREE亏损的1KEE分配型式。岩石学和地球化学特征揭示，Fe—Ti榴辉岩的原岩是变质的Fe—Ti辉长岩，是基性岩浆强烈分离结晶作用形成的超基性-基性-中酸性层状侵入体的特征组成部分。     

Fe2+在零价铁还原去除NO3-中的作用效应

零价铁（Fe0） 被广泛用于地下水中硝酸盐原位与异位修复,但二价铁（Fe2+） 的存在对具有氧化膜的Fe0还原硝酸盐的作用效应仍有待研究。以100 目的未经酸化的颗粒状零价铁作为还原剂,采用室内批试验方法,研究了Fe2+在零价铁还原去除NO3-系统中的作用效应。实验结果表明,Fe2+可显著提高Fe0对于NO3-的去除速率与去除效率,且Fe2+浓度越高,去除速率与效率越高;由于未经酸化的Fe0具有氧化膜,反应初期的NO3-还原速率较慢。Fe2+将零价铁表面的Fe2O3氧化膜转化为Fe3O4,加速电子由Fe0向NO3-的转移,促进NO3-还原。此外,在反应系统中加入Fe3O4,可进一步提高Fe0对于硝酸盐的去除能力,若Fe2+不存在,仅添加Fe3O4,NO3-的去除效率没有提高。     

湘西上震旦统层状硅质岩沉积环境的地球化学标志

湘西上震旦统层状硅质岩化学成分纯净，硅质矿物平均含量95％以上，且FeO/Fe2O3比值大于1，MnO/TiO2比值为6．1，P2O5含量极低。微量元素Sr/Ba比值小于1，稀土以总量低（5．64－31．54μg/g）和铈亏损为特征。硅质岩的δ^30Si值变化在0．0‰～0.7‰之间，硅质岩中有机碳含量较高，介于0．443％－1．993％之间，Pr/Ph比值小于1。硅质岩的上述特点反映其沉积大陆边缘斜坡半深海至大洋盆地深海环境中。     

在我国广西发现的钡毒铁石

1989年我们在广西德保矿区发现了钡毒铁石，其化学成分为（％）：BaO8．45，Fe2O335．10，As2O538．15，K2O0．14，Al2O30．07，H2O 18．48，总量为100．38。其理想矿物分子式为Ba0.5Fe4（AsO4）。（OH）4·7H2O，与德国产出的钡毒铁石的矿物分子式［BaFe4（AsO4）3（OH）5·5H2O］有一定的差异，是毒铁石［KFe4（AsO4）3（OH）4·7H2O］的钡端员矿物。该矿物是黄绿色、浅黄色，立方体晶形，硬度H=3，实测比重D=3．00，N=l．724～l．731，均质性，常见光性异常。粉晶X射线分析主要衍射强线（um）为：O．805（200）（99），0．563（220）（23），0．399（400）（47），O．326（422）（100），0284（44O）（73），0．241（542）（33），0．178（841）（23），等轴晶系，空间群为P43m，晶胞参数a=1．603nm。     

Phase relations between Ca3Fe 2 3 +Si3O12-Fe 3 2 +Fe 2 3 +Si3O12 garnet and CaFeSi2O6-Fe2Si2O6 pyroxene solid solutions

Editorial responsibility: J. Hoefs     

Compressibility of P2O5-Al2O3-Na2SiO3 melts

The effect of composition and temperature on the relaxed adiabatic bulk modulus of melts in the P₂O₅-Al₂O ₃-Na₂SiO₃ system have been investigated in the temperature range of 1140 to 1450 °C using ultrasonic interferometric methods at frequencies of 3, 5 and 7 MHz. The density of these melts was determined using Pt-double-bob Archimedean densitometry techiques. P₂O₅ is known to dramatically affect the structure and the chemical and physical properties of granitic and pegmatitic melts as a function of the peralkalinity of the melt. The physical results of the structural changes occurring in Na₂O-Al₂O₃-SiO₂ melt upon the addition of P₂O₅ are observed by variations in the properties such as density and compressibility. For the present peralkaline melts, the bulk modulus and density decrease with addition of 15 mol% P₂O₅, and increase with the addition of 15 mol% Al₂O₃. The addition of P₂O₅ to the present melts results in a larger increase in melt compressibility than that observed with increasing polymerization between Na₂SiO₃ and Na₂Si₂O₅ melts. This would suggest that not only is the polymerization of the melt increasing with the addition of P₂O₅ (Mysen et al. 1981; Nelson and Tallant 1984; Gan and Hess 1992), but that the tetrahedrally co-ordinated phosphorus complexes are influencing the bond lengths and energies within the melt structure; resulting in the structure becoming more compressible than expected, although incompressible (Vaughan and Weidner 1987) tetrahedral P₂O₅ polyhedra (Mysen et al. 1981; Gan and Hess 1992; Toplis et al. 1994) are being added to the melt structure.     

Surinamite analogs in the MgO-Ga2O3-GeO2 and MgO-Al2O3-GeO2 systems

New germanate analogs of the mineral surinamite, Mg₃Al₄BeSi₃O₁₆, have been synthesized with composition Mg₄A₄Ge₃O₁₆ (A=Al, Ga) and have been characterized by powder X-ray diffraction and transmission electron microscopy. The Al surinamite phase crystallizes with a primitive unit-cell (P2/n, a=10.153(1), b=11.708(2), c=9.920(1) Å, β=110.18 (2)° and Z=4) similar to that of the silicate mineral. The Ga surinamite-like phase crystallizes with a larger unit-cell (C2/c, a=10.308(2), b=23.690(5), c=10.057(l) Å, β=110.23 (2)° and Z=8). High-resolution electron microscopy has shown the common formation of intergrowths between the surinamite and sapphirine structures, illustrating the polysomatic structural relationship between them. Observations of disordered microstructures in the Al surinamite suggest the occurrence of a P2/n?C2/c transformation.     

Synthesis of Ca-tourmaline in the system CaO-MgO-Al2O3-SiO2-B2O3-H2O-HCl

Summary. ?Ca-tourmaline has been synthesized hydrothermally in the presence of Ca(OH)₂ and CaCl₂-bearing solutions of different concentration at T = 300–700 °C at a constant fluid pressure of 200 MPa in the system CaO-MgO-Al₂O₃-SiO₂-B₂O₃-H₂O-HCl. Synthesis of tourmaline was possible at 400 °C, but only above 500 °C considerable amounts of tourmaline formed. Electron microprobe analysis and X-ray powder data indicate that the synthetic tourmalines are essentially solid solutions between oxy-uvite, CaMg₃- Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O, and oxy-Mg-foitite, □(MgAl₂)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O. The amount of Ca ranges from 0.36 to 0.88 Ca pfu and increases with synthesis temperature as well as with bulk Ca-concentration in the starting mixture. No hydroxy-uvite, CaMg₃(MgAl₅)(Si₆O₁₈)(BO₃)₃(OH)₃(OH), could be synthesized. All tourmalines have < 3 Mg and > 6 Al pfu. The Al/(Al + Mg)-ratio decreases from 0.80 to 0.70 with increasing Ca content. Al is coupled with Mg and Ca via the substitutions Al₂□Mg₋₂Ca₋₁ and AlMg₋₁H₋₁. No single phase tourmaline could be synthesized. Anorthite ( + quartz in most runs) has been found coexisting with tourmaline. Other phases are chlorite, tremolite, enstatite or cordierite. Between solid and fluid, Ca is strongly fractionated into tourmaline ( + anorthite). The concentration ratio D = Ca(fluid)/Ca(tur) increases from 0.20 at 500 °C up to 0.31 at 700 °C. For the assemblage turmaline + anorthite + quartz + chlorite or tremolite or cordierite, the relationship between Ca content in tourmaline and in fluid with temperature can be described by the equation (whereby T = temperature in °C, Ca(tur) = amount of Ca on the X-site in tourmaline, Ca( fluid) = concentration of Ca²⁺ in the fluid in mol/l). The investigations may serve as a first guideline to evaluate the possibility to use tourmaline as an indicator for the fluid composition.

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Zusammenfassung. ?Synthese von Ca-Turmelin im System CaO-MgO-Al ₂ O ₃ -SiO ₂ -B ₂ O ₃ -H ₂ O-HCl Im System CaO-MgO-Al₂O₃-SiO₂-B₂O₃-H₂O-HCl wurde Ca-Turmalin hydrothermal aus Ca(OH)₂ and CaCl₂-haltigen L?sungen bei T = 300–700 °C und einem konstanten Fluiddruck von 200 MPa synthetisiert. Die Synthese von Turmalin war m?glich ab 400 °C, aber nur oberhalb von 500 °C bildeten sich deutliche Mengen an Turmalin. Elektronenstrahl-Mikrosondenanalysen und R?ntgenpulveraufnahmen zeigen, da? Mischkristalle der Reihe Oxy-Uvit, CaMg₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O, und Oxy-Mg-Foitit, □(MgAl₂)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O gebildet wurden. Der Anteil an Ca variiert zwischen 0.36 und 0.88 Ca pfu und nimmt mit zunehmender Synthesetemperatur und zunehmender Ca-Konzentration im System zu. Hydroxy-Uvit, CaMg₃(MgAl₅) (Si₆O₁₈)(BO₃)₃(OH)₃(OH), konnte nicht synthetisiert werden. Alle Turmaline haben < 3 Mg und > 6 Al pfu. Dabei nimmt das Al/(Al + Mg)- Verh?ltnis mit zunehmendem Ca-Gehalt von 0.80 auf 0.70 ab. Al ist gekoppelt mit Mg und Ca über die Substitutionen Al₂□Mg₋₂Ca₋₁ und AlMg₋₁H₋₁. Einphasiger Turmalin konnte nicht synthetisiert werden. Anorthit (+ Quarz in den meisten F?llen) koexistiert mit Turmalin. Andere Phasen sind Chlorit, Tremolit, Enstatit oder Cordierit. Ca zeigt eine deutliche Fraktionierung in den Festk?rpern Turmalin (+ Anorthit). Das Konzentrationsverh?ltnis D = Ca(fluid)/Ca(tur) nimmt von 0.20 bei 500 °C auf 0.31 bei 700 °C zu. Für die Paragenese Turmalin + Anorthit + Quarz mit Chlorit oder Tremolit oder Cordierit gilt folgende Beziehung zwischen Ca-Gehalt in Turmalin und Fluid und der Temperatur: (wobei T = Temperatur in °C, Ca(tur) = Anteil an Ca auf der X-Position in Turmalin, Ca(fluid) = Konzentration von Ca²⁺ im Fluid in mol/l). Die Untersuchungen dienen zur ersten Absch?tzung, ob Turmalin als Fluidindikator petrologisch nutzbar ist.

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Received July 24, 1998;/revised version accepted October 21, 1999     

Internally-Consistent Thermodynamic Data for Minerals in the System Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-SiO2-TiO2-H2O-CO2

Internally consistent standard state thermodynamic data arepresented for 67 minerals in the system Na₂O-K₂O-CaO-MgO-FeO-Fe₂O₃-Al₂O₃-SiO₂-TiO₂-H₂O-CO₂.The method of mathematical programming was used to achieve consistencyof derived properties with phase equilibrium, calorimetric,and volumetric data, utilizing equations that account for thethermodynamic consequences of first and second order phase transitions,and temperature-dependent disorder. Tabulated properties arein good agreement with thermophysical data, as well as beingconsistent with the bulk of phase equilibrium data obtainedin solubility studies, weight change experiments, and reversalsinvolving both single and mixed volatile species. The reliabilityof the thermodynamic data set is documented by extensive comparisons(Figs. 4–45) between computed equilibria and phase equilibriumdata. The high degree of consistency obtained with these diverseexperimental data gives confidence that the refined thermodynamicproperties should allow accurate prediction of phase relationshipsamong stoichiometric minerals in complex chemical systems, andprovide a reasonable basis from which activity models for mineralsmay be derived.     

Stability of the assemblage orthopyroxene-sillimanite-quartz in the system MgO-FeO-Fe2O3-Al2O3-SiO2-H2O

The stability of coexisting orthopyroxene, sillimanite and quartz and the composition of orthopyroxene in this assemblage has been determined in the system MgO-FeO-Fe₂O₃-Al₂O₃-SiO₂-H₂O as a function of pressure, mainly at 1,000° C, and at oxygen fugacities defined mostly by the hematite-magnetite buffer. The upper stability of the assemblage is terminated at 17 kbars, 1,000° C, by the reaction opx+Al-silicate gar+qz, proceeding toward lower pressures with increasing Fe/(Fe+Mg) ratio in the system. The lower stability is controlled by the reaction opx+sill+qz cord, which occurs at 11 kbars in the iron-free system but is lowered to 9 kbars with increasing Fe/(Fe+Mg). Spinel solid solutions are stabilized, besides quartz, up to 14 kbars in favour of garnet in the iron-rich part of the system (Fe/(Fe+Mg)0.30). Ferric-ferrous ratios in orthopyroxene are increasing with increasing ferro-magnesian ratio. At least part of the generally observed increase in Al content with Fe²⁺ in orthopyroxene is not due to an increased solubility of the MgAlAlSiO₆ component but rather of a MgFe³⁺AlSiO₆ component. The data permit an estimate of oxygen fugacity from the composition of orthopyroxene in coexistence with sillimanite and quartz.     

High temperature structural investigation of Na2O·0.5Fe2O3·3SiO2 and Na2O·FeO·3SiO2 melts and glasses

The structure of glasses and melts of Na₂O· 0.5Fe₂O₃·3SiO₂ and Na₂O·FeO·3SiO₂ compositions have been measured using high temperature Raman spectroscopy. For the oxidized sample it has been demonstrated that there is a close structural relationship between melt and glass. No coordination changes of Fe³⁺ with temperature and no new anionic species have been observed in the oxidized melt. The Raman spectra of the reduced sample clearly show a decrease in the degree of polymerization, as determined by the observation of the polarization character of the spectra and the details of the change of the Raman intensities during heating in hydrogen. Mössbauer spectra suggest that Fe³⁺ is tetrahedrally coordinated in the oxidized glass and part of the Fe²⁺ is tetrahedrally coordinated in the reduced glass.     

Phase relations in the systems Cu2S-PbS-Bi2S3 and Ag2S-PbS-Bi2S3 and their mineral assemblages

The phase diagrams of the systems Cu₂S-PbS-Bi₂S₃ and Ag₂S-PbS-Bi₂S₃ have been investigated in the present study. The paper is concerned with the complete solid solution between bismuthtite and aikinite above 300°C in the system Cu₂S-PbS-Bi₂S₃. The synthetic phases CuBi₃S₅ and Cu₃Bi₅S₉ have their solid solution ranges in the ternary system with 9 and 26 mole% PbS at maximum, respectively. A complete solid solution between PbS and AgBiS₂ divides the phase diagram of the system Ag₂S-PbS-Bi₂S₃ into two parts: Bi-rich and Ag-rich. All sulfosalt minerals and solid solutions, including pavonite ss, lillianite ss, heyovskyite and benjaminite are on the Bi-rich side. And divarant relations were found between pavonite ss -lillianite ss, benjaminite and bismuthtite as well as between lillianite ss -bismuthtite and galenobismutite. Synthetic experiments using LiCl-KCl flux technique show that when a minor amount of copper (less lwt.%) is added in, many of Ag-and Pb-bismuth sulfosalt minerals, for example, vikingite (Ag₅Pb₈Bi₁₃S₃₀), are synthesized successively, particularly at 400°C. So is heyrovskyite, which has a solid solution range with 3.7 mole% Cu₂S at maximum in the system Cu₂S-PbS-Bi₂S₃.