-
黝铜矿族(Cu12Sb4S13)矿物是热液矿床中常见的硫盐矿物,一般结构式为M(2)A6M(1)(B4C2)X(3)D4S(1)Y12S(2)Z(Biagioni et al.,2020a),由于存在多种等价和异价取代作用,而成为硫化物中最复杂的同型系列之一(Moëlo et al.,2008)。Biagioni et al.(2020a)根据A、B、D和Y的组成,将黝铜矿族分为:黝铜矿(Tetrahedrite)、砷黝铜矿(Tennantite)、银黝铜矿(Freibergite)、硒黝铜矿(Hakite)、硒砷黝铜矿(Giraudite)5个系列。此外,根据C的主要成分,黝铜矿族还可以分为:碲黝铜矿(Goldfieldite)、砷银黝铜矿(Arsenofreibergite)、诺雅黝银矿(暂译名)(Rozhdestvenskayaite)3个系列。
-
银黝铜矿系列(Freibergite)(Ag,Cu)12Sb4S13是最常见的银矿物之一,不仅有着重要的经济价值,同时其银的含量也是成矿温度的指标参数,可间接反映银(铅、锌)矿体赋存部位及矿石质量,对矿床研究有着重要意义(Wang Guofu,2008)。更为重要的是(Ag6)4+这一特殊结构因其在催化、化学传感和光电功能材料的突出性能,已经成为银簇团研究领域的热点❶。截至2021年,银黝铜矿系列矿物已知成员有6个,即铁银黝铜矿(暂译名)(Argentotetrahedrite-(Fe))Ag6(Cu4Fe2)Sb4S13(Peterson et al.,1986; Welch et al.,2018)、空铁银黝铜矿(暂译名)(Kenoargentotetrahedrite-(Fe))Ag6(Cu4Fe2)Sb4S12□(Criddle et al.,1986; Welch et al.,2018)、镉银黝铜矿(Argentotetrahedrite-(Cd))Ag6(Cu4Cd2)Sb4S13(Repstock et al.,2016)、锌银黝铜矿(暂译名)(Argentotetrahedrite-(Zn))Ag6(Cu4Zn2)Sb4S13(Miyawaki et al.,2021)、空锌银黝铜矿❶(Kenoargentotetrahedrite-(Zn))Ag6(Cu4Zn2)Sb4S12□(Miyawaki et al.,2021)及汞银黝铜矿。
-
作为新矿物种的汞银黝铜矿,其矿物和命名已得到国际矿物协会新矿物命名与分类委员会(IMACNMNC)的批准(批准号:IMA 2020-079)。汞银黝铜矿的全型标本,保存于中国地质博物馆(馆藏编号:M16114)。该文描述新矿物汞银黝铜矿的产状、化学成分、物理性质、晶体结构等特征,并讨论其形成机制和地质学意义。
-
1 产状、共生矿物和成因
-
汞银黝铜矿发现于湘黔汞矿带北段之保靖东坪Hg-Ag矿床(109°37′10.8″E,28°36′05.1″N)。矿床中汞银矿化体主要呈透镜状、囊状赋存于下寒武统清虚洞组(∈1q)含碳泥质显微晶粒白云岩的断裂破碎带内。矿体总体走向NE—NNE,倾向SE,倾角20°~45°,长0.4~1.65 km,宽15~110 km,厚1.27~1.53 m,平均Hg含量0.12%~0.17%,Ag含量100.82 g/t❷。矿石矿物主要有灰硒汞矿、黑辰砂、辉锑银矿、硫锑银矿、黄铁矿等,脉石矿物主要有石英、方解石等(图1)。矿石多具自形、半自形、他形粒状结构,以脉状、浸染状构造为主。与汞银矿化关系密切的蚀变包括碳酸盐化、硅化等。汞银黝铜矿与灰硒汞矿、黑辰砂、含汞自然银、硫锑银矿、辉锑银矿、脆银矿、闪锌矿和方铅矿共生,产于石英、方解石脉中(图1、2)。
-
驰名中外的湘黔汞矿带位于中国西南大面积低温成矿域,探明储量约占全国汞矿总储量的50%,是我国最重要的汞矿资源基地(Yan Junping et al.,1989; Bao Yumin et al.,1999; Wang Jiasheng et al.,2010),带内汞矿床的母源为某些含汞建造,其形成与有机质或小构造有关(Yan Junping et al.,1989; Wang Jiasheng et al.,2010)。已有研究表明,湘黔汞矿带北段的东坪Hg-Ag矿床为中低温热液脉型矿床,汞银黝铜矿形成于热液活动后期,温度为100~215℃(Chen Dianfen et al.,1991)。
-
图1 东坪Hg-Ag矿床矿石照片(汞银黝铜矿及共生的灰硒汞矿、黑辰砂、辉锑银矿、硫锑银矿等金属矿物集合体呈浸染状、脉状分布在石英脉中)
-
Fig.1 The ore photograph of Dongping Hg-Ag deposit (Argentotetrahedrite- (Hg) and its associated metallic minerals such as tiemannite, metacinnabar, miargyrite and andorite are distributed in the quartz vein in the form of disseminated and veined)
-
2 物性与光学性质
-
汞银黝铜矿单晶体粒度约为5~20 μm,呈粒径20~300 μm的粒状、片状集合体产出。汞银黝铜矿为黑色,条痕红黑色,金属光泽,不具荧光性和磁性,无解理,性脆,断口不规则。在显微镜下用微粒方解石和萤石刻划汞银黝铜矿表面,估测其摩氏硬度值为3~3.5。其计算密度:5.578 g/cm3。
-
汞银黝铜矿为不透明矿物,显微镜下呈黄—灰绿色,无双反射、多色性及各向异性,无内反射。以SiC为标样,利用Leica DM2500p及J& M Tidas MSP400分光光度计,测得汞银黝铜矿的反射率如表1所示。
-
3 化学成分
-
汞银黝铜矿的化学成分分析在中南大学地球科学与信息物理学院完成,所用样品为东坪Hg-Ag矿床矿石磨制成的探针片,测试仪器为EPMA-1720型(日本岛津公司),测试条件为:加速电压15 kV,电流10 nA,电子束斑直径1 μm。测试结果如表2所示。
-
图2 东坪Hg-Ag矿床汞银黝铜矿的产状和矿物组合
-
Fig.2 The occurrence and mineral association of argentotetrahedrite- (Hg) from the Dongping Hg-Ag deposit, Baojing County, Hunan Province
-
(a~c)—显微照片(反射单偏光);(d)—背散射图像; adr—硫锑银矿; ath—汞银黝铜矿; cal—方解石; gn—方铅矿; hag—含汞自然银; mcb—黑辰砂; mgy—辉锑银矿; py—黄铁矿; qz—石英; sp—闪锌矿; tim—灰硒汞矿
-
(a~c) —Reflected-light photomicrograph; (d) —back scattered electron image; adr—andorite; ath—argentotetrahedrite- (Hg) ; cal—calcite; gn—galena; hag—mercurian silver; mcb—metacinnabar; mgy—miargyrite; py—pyrite; qz—quartz; sp—sphalerite; tim—tiemannite
-
根据总原子数(29 apfu),按照Biagioni et al.(2020a)总结的黝铜矿的一般结构式:M(2)A6M(1)(B4C2)X(3)D4S(1)Y12S(2)Z,汞银黝铜矿的经验化学式可以写成:M(2)(Ag3.39Cu2.61)Σ6M(1)[Cu3.75(Hg1.66Zn0.32Fe0.14)Σ2.12]Σ5.87X(3)(Sb3.98As0.10) Σ4.08(S13.02Se0.04) Σ13.06。其简化式则为:(Ag,Cu)6[Cu4(Hg,Zn,Fe)2]Sb4S13。理想化学式为:Ag6(Cu4Hg2)Sb4S13。
-
4 X射线结晶学研究
-
4.1 单晶X射线衍射及晶体结构
-
在中南大学地球科学与信息物理学院,利用Rigaku XtaLAB Synergy单晶X射线衍射仪,收集了汞银黝铜矿的衍射强度数据。实验条件为MoKα射线(λ=0.07107 nm),石墨单色器,晶体中心与Hypix6000检测器的距离35 mm,管压50 kV,管流1 mA,帧曝光时间205 s,获得晶胞参数:a =1.06511(2)nm,V =1.20832(5)nm3,Z =2。使用SHELXT(Sheldrick,2015a)解出汞银黝铜矿的晶体结构模型,空间群I 3m,再应用SHELXL(Sheldrick,2015b)和Olex2(Dolomanov et al.,2009)程序进行结构精修,精修数据归纳于表3。对294个独立衍射点(I >4σ)和1197个总衍射点进行了各向异性位移参数的全矩阵最小二乘法精修,最终的精修因子为R1(F2)=2.80%,wR2(F2)=6.59%(I >4σ)和R1(F2)=2.94%,wR2(F2)=6.62%(表3)。精修过程中,对S、Sb位置进行了自由占位精修,而Ag、Cu、Hg、Fe、Zn则手动精修至最小R1值,并与化学成分符合。获得的汞银黝铜矿晶体的原子位置和各向异性位移参数如表4、5所示,代表性键长和键角如表6所示,晶体结构如图3所示。
-
注:① 11测点电子探针分析均值。
-
精修结果表明,汞银黝铜矿的晶体结构与黝铜矿族矿物的晶体结构类同。Biogioni et al.(2020a)对黝铜矿族矿物的晶体化学和命名进行了系统阐述,提出其一般结构式为M(2)A6M(1)(B4C2)X(3)D4S(1)Y12S(2)Z,并提出根据二价阳离子C位的离子种类划分出独立矿物。在汞银黝铜矿中,四面体配位S(1)、八面体配位S(2)和三角锥形配位X(3)分别被S和Sb完全占位(表4)。三角形配位M(2)以 Ag+(3.39 apfu)和Cu+(2.61 apfu)离子占位为主,四面体配位M(1)占位离子有Cu+(3.96 apfu)、Hg2+(1.56 apfu)、Zn2+(0.29 apfu)和Fe2+(0.19 apfu)(表4、图3)。S(2)位明显具有较大的各向异性位移参数,这是银黝铜矿系列矿物中常见的共有现象,可能与Ag在M(2)的占位导致S原子的无序有关(Peterson et al.,1986)。
-
图3 汞银黝铜矿的晶体结构(使用Olex2(Dolomanov et al.,2009)和VESTA(Momma et al.,2011)程序绘制)
-
Fig.3 The crystal structure of argentotetrahedrite- (Hg) plotted using Olex2 (Dolomanov et al., 2009) and VESTA (Momma et al., 2011)
-
(a)—原子的位置和连通性;(b)—晶胞组成、M1四面体(粉红色围体)和M2三角形(蓝色围体)
-
(a) —Showing the sites of atoms and connectivity; (b) —showing the unit cell contents and the M1 tetrahedra and M2 triangles
-
4.2 粉晶X射线衍射分析
-
在Rigaku XtaLAB Synergy衍射仪上按粉晶衍射甘多费模式收集(MoKα射线,50 kV,1 mA,图桢曝光时间88 s),得到粉晶数据见表7,与结构计算得到的粉末衍射谱一致,如图4。利用Holland et al.(1997)软件得到精修的晶胞参数为:空间群为 I 3m(No.217),a =1.06330(3)nm,V =1.20217(12)nm3,Z =2。
-
5 矿物命名
-
Biagioni et al.(2020a)通过黝铜矿超族的矿物化学、结晶学研究,提出并经CNMNC(Miyawaki et al.,2019)批准的命名规则。根据该规则,将该矿物命名为汞银黝铜矿(argentotetrahedrite-(Hg))。该矿物是黝铜矿族中Ag占据M(2)、Hg作为电荷补偿占据M(1)位的独立矿物种。
-
6 与同族矿物的关系
-
汞银黝铜矿是黝铜矿族银黝铜矿系列的一员,其特征为Ag占据M(2)、Hg作为电荷补偿占据M(1)位。表8展示了汞银黝铜矿与黝铜矿族其他成员的对比。由表可知,Ag、Hg的加入可使黝铜矿的晶胞参数a和晶胞体积V,以及M(1)-S1、M(2)-S2、M(2)-S1的键长显著增大,特别是,Hg与M(1)-S1的键长、Ag与M(2)-S2、M(2)-S1的键长呈正相关。
-
注:①为本次研究; ②据Welch et al.(2018); ③据Biagioni et al.(2020b)。
-
图4 汞银黝铜矿粉晶X射线衍射图
-
Fig.4 Powder X-ray diffraction pattern of argentotetrahedrite- (Hg)
-
早在19世纪就有关于汞黝铜矿的报道(如:Kersten,1843; Weidenbusch,1849; Palache et al.,1951)。Kenngott(1853)将产于奥地利蒂罗尔州施瓦茨(Schwaz,Tyrol)的富汞黝铜矿命名为“schwazite”,但遭到了Arlt et al.(1998)的质疑。众多学者对汞黝铜矿的化学成分(Criddle et al.,1993; Chen Luming et al.,1994; Foit et al.,2001; Grammatikopoulos et al.,2005; Velebil,2014)和结构(Kalbskopf,1971; Kaplunnik et al.,1980; KaranoviAc' et al.,2003; Foit et al.,2004)进行了研究。然而,只有Atanasov(1975)报道了保加利亚斯塔拉-普拉尼纳(Stara-Planina mountains)山脉西部Chiprovtsi铅银矿床中含Hg、Ag的黝铜矿样品的成分(Cu6.88Ag2.96(Hg1.83Zn0.17)Σ2.00(Sb3.36As0.71)Σ4.07S13.09)和粉晶衍射数据,与本研究中的汞银黝铜矿接近,但在缺乏单晶X射线衍射研究的情况下,不能证实是否为同一物质。
-
虽然在有关黑辰砂和灰硒汞矿或选矿技术的一些文章中提到了本研究中含汞和含银的黝铜矿(Chen Dianfen et al.,1991; Huang Zhongqi,1991; Xiang Ping et al.,2005),但它们都没有提供化学和结构数据。因此,本文首次提出了汞银黝铜矿完整的化学和结构数据,它是黝铜矿族中Ag占据M(2)、Hg作为电荷补偿占据M(1)位的独立矿物。
-
7 意义
-
汞银黝铜矿作为黝铜矿族矿物新种,是因为其M(2)位以Ag为主、Hg作为电荷补偿占据M(1)位,这是汞银黝铜矿殊异于黝铜矿族所有已知成员的独特之处。
-
汞银黝铜矿的发现,丰富了黝铜矿族银黝铜矿系列矿物种类数与研究资料。在东坪矿床,汞银黝铜矿是主要的矿石矿物,是Cu、Ag、Hg元素的重要回收对象,因此,汞银黝铜矿的发现对深入研究湘黔汞矿带的矿床成因、提升矿床经济价值具有重要意义。
-
致谢:湖南株洲华旗科技公司向平先生及湖南保靖万家黄金茶业公司陈光杰先生协助采样,两位匿名审稿专家对论文提出非常宝贵的修改意见。
-
注释
-
❶ 曲凯.2021.天津地调中心发现自然界新矿物——空锌银黝铜矿. 中国地质调查局网站.
-
❷ 龙国华,谢顺赞,彭国进.1995. 湖南省保靖县东坪汞银矿普查报告.
-
参考文献
-
Arlt T, Diamond L W. 1998. Composition of tetrahedrite-tennantite and ‘schwazite’ in the Schwaz silver mines, North Tyrol, Austria. Mineralogical Magazine, 62: 801~820.
-
Atanasov V A. 1975. Argentian mercurian tetrahedrite, a new variety, from the Chiprovtsi ore deposit, western Stara-Planina mountains, Bulgaria. Mineralogical Magazine, 40: 233~237.
-
Bao Yumin, Wan Rongjiang, Bao Zhenxiang. 1999. Discussion of the mercury mineralization related to the mercury metallogeic belt of Hunan-Guizhou Province. Beijing Geology, 2: 5~12 (in Chinese with English abstract).
-
Biagioni C, GeorgeL L, Cook N J, Makovicky E, Moëlo Y, Pasero M, Sejkora J, Stanley C J, Welch M D, Bosi F. 2020a. The tetrahedrite group: nomenclature and classification. American Mineralogist, 105: 109~122.
-
Biagioni C, Sejkora J, Musetti S, Velebil D, Pasero M. 2020b. Tetrahedrite-(Hg), a new “old” member of the tetrahedrite group. Mineralogical Magazine, 84: 584~592.
-
Chen Dianfen, Sun Shuqiong. 1991. Metacinnabar and tiemannite in the Hunan-Guizhou mercury zone. Acta Petrologica et Mineralogica, 10: 58~63 (in Chines with English abstract).
-
Chen Luming, Zhang Qifa. 1994. A study on mercurian tetrahedrite. Guizhou Science, 12(4): 9~10 (in Chinese without English abstract).
-
Criddle A J, Stanley C J. 1986. The Quantitative Data File for Ore Minerals of the Commission on Ore Microscopy of the International Mineralogical Association (2nd edition). British Museum (Natural History), 420.
-
Criddle A J, Stanley C J. 1993. Quantitative Data File for Ore Minerals (third issue). London: Chapman & Hall.
-
Dolomanov O V, Bourhis L J, Gildea R J, Howard J A K, Puschmann H. 2009. A complete structure solution, refinement and analysis program. Journal of Applied Crystallography, 42: 339~341.
-
Foit F F, Ulbricht M E. 2001. Compositional variation in mercurian tetrahedrite-tennantite from the epithermal deposits of the Steens and Pueblo Mountains, Harney County, Oregon. Canadian Mineralogist, 39: 819~830.
-
Foit F F, Hughes J M. 2004. Structural variations in mercurian tetrahedrite. American Mineralogist, 89(1): 159~163.
-
Grammatikopoulos T, Roth T, Valeyev O. 2005. Compositional variation in Hg-Ag rich tetrahedrite from the polymetallic Eskay Creek deposit, British Columbia, Canada. Neues Jahrbuch für Mineralogie Abhandlungen, 181: 281~292.
-
Holland T J B, Redfern S A T. 1997. Unit cell refinement from powder diffraction data: the use of regression diagnostics. Mineralogical Magazine, 61: 65~77.
-
Huang Zhongqi. 1991. Onofrite in the Dongping mercury deposit, Baojing, Hunan, China. Acta Mineralogica Sinica, 1(3): 274~278 (in Chinese without English abstract).
-
Kalbskopf R. 1971. Die koordination des quecksilbers in Schwazit. Tschermaks Mineralogische und Petrographische Mitteilungen, 16: 173~175.
-
Kaplunnik L N, Pobedimskaya E A, Belov N V. 1980. Crystal structure of schwatzite, (Cu4. 4Hg1. 6)Cu6Sb4S12. Soviet Physics Crystallography, 25: 508~509 (in Russian).
-
Karanović L, Cvetković L, Poleti D, Balić - Žunić T, Makovicky E. 2003. Structural and optical properties of schwazite from Dragodol (Serbia). Neues Jahrbuch für Mineralogie Monatshefte, 11: 503~520.
-
Kenngott G A. 1853. Das Mohs'sche Mineralsystem, dem Gegenwärtigen Standpunkte der Wissenschaft Gemäss Bearbeitet. Wien: Gerol & Sohn.
-
Kersten C. 1843. Untersuchung eines quecksilberhaltigen Fahlerzes von Val di Castello in Toscana. Annalen der Physik, 135: 131~135.
-
Miyawaki R, Hatert F, Pasero M, Mills S J. 2019. New minerals and nomenclature modifications approved in 2019. Mineralogical Magazine, 83: 323~328.
-
Miyawaki R, Hatert F, Pasero M, Mills S J. 2021. IMA Commission on New Minerals, Nomenclature and Classification (CNMNC)-Newsletter 59. European Journal of Mineralogy, 33(1): 139~143.
-
Moëlo Y, Makovicky E, Mozgova N N, Jambor J L, Cook N, Pring A, Paar W H, Nickel E H, Graeser S, Karup-Møller S, Balic-Zunic T, Mumme W G, Vurro F, Topa D. 2008. Sulfosalt systematics: a review. Report of the sulfosalt sub-committee of the IMA Commission on Ore Mineralogy. European Journal of Mineralogy, 20(1): 7~46.
-
Momma K. Izumi F. 2011. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. Journal of Applied Crystallography, 44: 1272~1276.
-
Palache C, Berman H, Frondel C. 1951. The system of mineralogy of James Dwing Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons Inc. , New York, 7th edition revised and enlarged, 1124, 532~534.
-
Peterson R C, Miller I. 1986. Crystal structure and cation distribution in freibergite and tetrahedrite. Mineralogical Magazine, 50: 717~721.
-
Repstock A, Voudouris P, Zeug M, Melfos V, Zhai M, Li H, Kartal T, Matuszczak J. 2016. Chemical composition and varieties of fahlore-group minerals from Oligocene mineralization in the Rhodope area, southern Bulgaria and northern Greece. Mineralogy and Petrology, 110: 103~123.
-
Sheldrick G M. 2015a. SHELXT-Integrated space-group and crystal structure determination. Acta Crystallographica, A71: 3~8.
-
Sheldrick G M. 2015b. Crystal structure refinement with SHELX. Acta Crystallographica, C71: 3~8.
-
Velebil D. 2014. A contribution to knowledge of chemistry of mercurian tetrahedrites: localities Jedová hora (Czech Republic), Rudňany, Rožňava, Nižná Slaná, Slovinky (Slovakia) and Maškara (Bosnia and Herzegovina). Bulletin Mineralogickopetrologického oddělení Národního Muzea v Praze, 22: 131~143 (in Czech).
-
Wang Jiasheng, Wen Hanjie, Shi Shaohua. 2010. Characteristics and implications of REE, carbon and oxygen isotopes of hydrothermal calcite from the mercury metallogenic belt in Hunan and Guizhou Provinces, China. Acta Mineralogica Sinica, 30(2): 185~193 (in Chinese with English abstract).
-
Weidenbusch H. 1849. Analyse des quecksilberhaltigen Fahlerzes von Schwatz in Tyrol. Annalen der Physik, 152: 86~88.
-
Welch M D, Stanley C J, Spratt J, Mills S J. 2018. Rozhdestvenskayaite Ag10Zn2Sb4S13 and argentotetrahedrite Ag6Cu4(Fe2+, Zn)2Sb4S13: two Ag-dominant members of the tetrahedrite group. European Journal of Mineralogy, 30: 1163~1172.
-
Xiang Ping, Niu Yinjian, Feng Qiming, Ou Leming, Huang Xin. 2005. Research on silver recovery of Dongping mercury-containing silver ore. Metal Mine, (suppl): 406~410 (in Chinese without English abstract).
-
Yan Junping, Liu Ping. 1989. Geological Features and Genesis of the Mercury Deposits of Guizhou Province· Geology of Mercury Deposits of Guizhou Province. Beijing: Geological Publishing House, 1~56 (in Chinese with English abstract).
-
鲍珏敏, 万溶江, 鲍振襄. 1999. 湘黔汞矿带相关成矿问题的讨论. 北京地质, 2: 5~12.
-
陈殿芬, 孙淑琼. 1991. 湘黔汞矿带中的黑辰砂和硒汞矿. 岩石矿物学杂志, 10: 58~62.
-
陈露明, 张启发. 1994. 汞黝铜矿的研究. 贵州科学, 12(4): 9~10.
-
王国富. 2008. 中低温热液铅锌银(金)矿床中银黝铜矿的标型特征. 黑龙江科技信息, (24): 38.
-
王加昇, 温汉捷, 石少华. 2010. 湘黔汞矿带脉石矿物方解石稀土元素、碳氧同位素特征及其指示意义. 矿物学报, 30(2): 185~193.
-
向平, 钮因健, 冯其明, 欧乐明, 黄鑫. 2005. 东坪含汞银矿提高银回收率的研究. 金属矿山, 406~410.
-
严钧平, 刘平. 1989. 贵州汞矿地质特征及成因·贵州汞矿地质. 北京: 地质出版社, 1~56.
-
黄中岐. 1991. 湖南保靖东坪汞矿中的含硒黑辰砂. 矿物学报, 1(3): 274~278.
-
摘要
作为黝铜矿族矿物的新成员,汞银黝铜矿(Argentotetrahedrite-(Hg),IMA 2020-079), Ag6(Cu4Hg2)Sb4S13,发现于湘黔汞矿带北段之保靖东坪Hg-Ag矿床中,是该矿床的主要矿石矿物和回收对象。汞银黝铜矿单晶晶体尺寸约为5~20 μm,呈粒径20~300 μm的粒状、片状集合体产出,与灰硒汞矿、黑辰砂、含汞自然银、硫锑银矿、辉锑银矿、脆银矿、闪锌矿和方铅矿共生,产于石英、方解石脉中。汞银黝铜矿为黑色,条痕红黑色,金属光泽,无荧光性和磁性,无解理,性脆,断口不规则。矿物的摩氏硬度值为3~3.5,计算密度为5.578 g/cm3。汞银黝铜矿的化学成分:Ag 17.79%;Cu 19.65%;Hg 16.17%;Zn 1.01%;Fe 0.37%;Sb 23.56%;As 0.36%;Se 0.15%;S 20.31%,总量99.52%。依据晶体结构精测和总原子数(29 apfu),得到汞银黝铜矿简化晶体化学式:Ag6(Cu4Hg2)Sb4S13。根据1197个衍射点的单晶衍射数据确定了汞银黝铜矿的晶体结构(精修因子R 1=0.0294),属立方晶系,空间群为I 3m,a =1.06330(3) nm,V =1.20217(11) nm3,Z =2。其结构中,四面体配位S(1)、八面体配位S(2)和三角锥形配位X(3)分别被S和Sb完全占位。三角形配位M(2)以Ag+ (3.39 apfu)和Cu+ (2.61 apfu)离子占位,四面体配位M(1)占位离子有Cu+ (3.96 apfu)、Hg2+ (1.56 apfu)、Zn2+ (0.29 apfu)和Fe2+ (0.19 apfu),其M(2)位以Ag为主、Hg作为电荷补偿占据M(1)位。
Abstract
Argentotetrahedrite-(Hg) (IMA 2020-079), Ag6(Cu4Hg2)Sb4S13 is a new member of tetrahedrite-group of minerals found in the Dongping Hg-Ag deposit, Baojing County, northern section of the Hunan-Guizhou mercury metallogenic belt. It is the main ore mineral and recovery object of the deposit. A single crystal of argentotetrahedrite-(Hg) is around 5~20 μm, and occurs as granular and patchy agglomerate 20 to 300 μm in size. It occurs in association with tiemannite, metacinnabar, mercurian silver, andorite, miargyrite, stephanite, sphalerite and galena in quartz and calcite vein. Argentotetrahedrite-(Hg) exhibits a black colour with a reddish black streak and metallic lustre. The mineral is none fluorescence, magnetism and cleavage, brittle in tenacity, and has irregular fracture. The Morse hardness is 3~3.5. The calculated density is 5.578 g/cm3 on the basis of empirical formula and unit cell volume refined from single-crystal XRD data. The chemical composition is Ag 17.79%; Cu 19.65%; Hg 16.17%; Zn 1.01%; Fe 0.37%; Sb 23.56%; As 0.36%; Se 0.15%; S 20.31%, total 99.52%. On the basis of crystal refinement and total atoms=29 apfu, the crystal-chemical formula of argentotetrahedrite-(Hg) is Ag6 (Cu4Hg2)Sb4S13. According to the single crystal diffraction data of 1197 reflections, the crystal structure of argentotetrahedrite-(Hg) is determined (refinement factor R1=0.0294). It is cubic, space group I m, unit-cell parameters a =1.06330(3) nm, V =1.20217(11) nm3, Z =2. In argentotetrahedrite-(Hg), the tetrahedrally coordinated site S(1), the octahedrally coordinated site S(2), and the tri-pyramidally coordinated site X(3) are fully occupied by S and Sb respectively. The triangularly coordinated site M(2) is dominated by Ag+ (3.39 apfu) over Cu+ (2.61 apfu) and the tetrahedrally coordinated site M(1) is occupied by Cu+ (3.96 apfu), Hg2+ (1.56 apfu), Zn2+ (0.29 apfu), Fe2+ (0.19 apfu). It is characterized both by Ag dominance in M(2) and Hg dominance for charge compensation in M(1).