Drey

Salisbury, United Kingdom
Salisbury, United Kingdom

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Turner R.W.,Drey | Siidra O.I.,Saint Petersburg State University | Krivovichev S.V.,Saint Petersburg State University | Stanley C.J.,Natural History Museum in London | Spratt J.,Natural History Museum in London
Mineralogical Magazine | Year: 2012

Rumseyite, ideally [Pb2OF]Cl, is a new mineral species which is associated with calcite, cerussite, diaboleite, hydrocerussite and undifferentiated Mn oxides in a small cavity in 'hydrocerussite' from a manganese pod at Merehead quarry, Somerset, England. Rumseyite is tetragonal, I4/mmm, a = 4.065(1), c = 12.631(7) Å, V = 208.7(1) Å3, Z = 2. The mineral is translucent pale orange-brown with a white streak and vitreous lustre. It is brittle with perfect {100} cleavage; D calc = 7.71 g cm-3 (for the ideal formula, [Pb2OF]Cl). The mean refractive index in air at 589 nm is 2.15. The six strongest reflections in the X-ray powder-diffraction pattern [d meas in Å, (I rel), (hkl)] are as follows: 2.923(100)(013), 2.875(68)(110), 3.848(41)(011), 6.306(17)(002), 1.680(14)(123), 2.110(12)(006). The crystal structure of rumseyite is based on alternating [OFPb2] and Cl layers. Rumseyite is related to other layered Pb oxyhalides. Fluorine and oxygen are statistically disordered over one crystallographic site. Rumseyite is named in honour of Michael Scott (Mike) Rumsey (1980-), Curator and Collections Manager at the NHM (London), who discovered the mineral. The mineral and name have been approved by the IMA Commission on New Mineral Names and Classification (IMA 2011-091). The holotype specimen is in the collections of the Natural History Museum, London (specimen number BM1970,110). © 2012 Mineralogical Society.


Turner R.,Drey | Siidra O.I.,Saint Petersburg State University | Rumsey M.S.,Natural History Museum in London | Krivovichev S.V.,Saint Petersburg State University | And 2 more authors.
Mineralogical Magazine | Year: 2012

Two new lead oxychloride minerals, hereroite [Pb 32(O, & ) 21](AsO 4) 2((Si, As, V, Mo)O 4) 2Cl 10 and vladkrivovichevite [Pb 32O 18][Pb 4Mn 2O]Cl 14(BO 3) 8 •2H 2O occur in association with asisite, damaraite, kombatite, sahlinite, copper, quartz, barysilite, Mn silicates and a number of Mn oxyhydroxide minerals on a specimen from the Kombat mine in Namibia. The minerals formed as late-stage products of hydrothermal reworking of primary sulfide minerals. Hereroite is monoclinic, C2/c with a = 23.14(1),b = 22.65(1), c = 12.39(1) Å, b = 102.00(5)°, V = 6351.6(41) Å 3 from powder-diffraction data and a = 23.139(4), b = 22.684(4), c = 12.389(2) Å, b = 102.090(3)°, V = 6358.8(18) Å 3 from single-crystal data. It is bright orange, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 8.15 g cm -3. The mean refractive index in air at 589 nm is 2.38. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.982(100)(55̄1); 2.795(47)(802̄); 1.986(24)(88̄2̄); 1.641(24)(11.5̄.5̄); 3.512(23)(612̄); 3.901(21)(511). Hereroite is named for the Herero people, one of the indigenous tribal groupings in the region where the Kombat mine is located. Vladkrivovichevite is orthorhombic,Pmmn witha = 12.87(5),b = 27.7(4),c = 11.46(3) Å,V = 4080.1(5) Å 3, from powder-diffraction data anda = 12.759(1),b = 27.169(4),c = 11.515(1) Å,V = 3992.0(9) Å 3, Z = 2, from single-crystal data. It is pale greenish yellow, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 7.40 g cm -3. The mean refractive indices in air at 589 nm are 2.30 and 2.34. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.860(100)(370); 2.733(84)(073); 3.707(49)(073); 3.068(37)(401); 2.075(32)(473); 1.601(32)(3.14.3). Vladkrivovichevite is named in honour of Prof. Dr Vladimir Gerasimovich Krivovichev (b. 24.04.1946), Head of the Department of Mineralogy, Geological Faculty, St Petersburg State University. The crystal structures of hereroite and vladkrivovichevite consist of alternating litharge-like O - Pb double layers and chlorine sheets and both are structurally related to other layered lead oxychlorides. In hereroite, tetrahedral AsO 4 and (Si, As, V, Mo)O 4 groups locate in defects within the O - Pb block, which combines square 'symesite-type' and double-square 'kombatite-type' cavities in its crystal structure. The structure of vladkrivovichevite is based on O - Pb derivative blocks with the interlayer occupied by Cl - anions and oxocentred OPb 4Mn 2 octahedra whose eight triangular faces are capped by triangular borate anions, BO 3- 3. © 2012 Mineralogical Society.


Siidra O.I.,Saint Petersburg State University | Krivovichev S.V.,Saint Petersburg State University | Turner R.W.,Drey | Rumsey M.S.,Natural History Museum in London | Spratt J.,Natural History Museum in London
American Mineralogist | Year: 2013

The crystal structure of hereroite, a new complex lead oxychloride mineral from the Kombat Mine, Grootfontein, Namibia, has been solved by direct methods and refined to R1 = 0.054 for 6931 unique observed reflections. The mineral is monoclinic C2/c, a = 23.139(4), b = 22.684(4), c = 12.389(2) Å, β = 102.090(3)°, and V = 6358.8(18) Å3. The structure contains 16 independent Pb sites in strongly asymmetric coordination by O and Cl atoms. There are two tetrahedral sites, from which one (As) is occupied solely by As, whereas the second (T) has the mixed occupancy of [Si 0.48As0.29V0.15Mo0.09]. There are in total 21 O sites. The O1-O8 sites belong to the AsO4 and TO 4 tetrahedral oxyanions. The other O atoms (O9-O20) are tetrahedrally coordinated by Pb atoms, thus being central for the OPb4 oxocentered tetrahedra. The OPb4 tetrahedra share edges to form the [O 21Pb32]22+ layers that can be described as derivatives of the [OPb] layer from the structure of tetragonal PbO (litharge). The [O21Pb32]22+ layer in hereroite can be obtained from the [OPb] layer by removal of blocks of oxocentered tetrahedra, which results in formation of double-square sevenfold and square fourfold cavities. The cavities are occupied by the AsO4 and TO4 tetrahedra, respectively. The topology of the [O21Pb 32]22+ layer is complex and can be described as a combination of modules extracted from the layers of OPb4 tetrahedra present in the structures of kombatite and symesite. The topological functions of tetrahedra within the layer are analyzed using the square lattice method, which shows that each symmetry-independent tetrahedron has its own topological function in the layer construction. The structure of hereroite belongs to the 2:1 type of layered Pb oxyhalides and consists of alternating PbO-type layers and Cl sheets oriented parallel to the (010) plane.


Siidra O.I.,Saint Petersburg State University | Krivovichev S.V.,Saint Petersburg State University | Turner R.W.,Drey | Rumsey M.S.,Natural History Museum in London | Spratt J.,Natural History Museum in London
American Mineralogist | Year: 2013

The crystal structure of vladkrivovichevite, a new complex lead oxychloride mineral from the Kombat Mine, Grootfontein, Namibia, has been solved by direct methods and refined to R1 = 0.048 for 3801 unique observed reflections. The mineral is orthorhombic, Pmmn, a = 12.759(1), b = 27.169(4), c = 11.515(1) Å, and V = 3992.0(9) Å3. The structure of vladkrivovichevite belongs to a novel type of layered Pb oxychloride structure. The structure contains 12 symmetrically independent Pb sites. All Pb sites have strongly asymmetric coordination. Two B atoms form slightly distorted BO 3 triangles. One symmetrically independent Mn atom forms five Mn-O bonds and one Mn-Cl bond by forming MnO5Cl octahedra. The O1, O2, O10, O11, and O12 atoms are tetrahedrally coordinated by four Pb atoms each, forming OPb4 oxocentered tetrahedra. The O7 site has a remarkable octahedral coordination, consisting of four Pb and two Mn atoms. The O1Pb 4, O2Pb4, O10Pb4, and O11Pb4 tetrahedra share common edges to produce bands interconnected by O12Pb 4 tetrahedra, forming a [O18Pb32]28+ layer. A O7Pb4Mn2 heterometallic oxocentered octahedron serves as the core of the [OPb4Mn2Cl2(BO 3)8]16- clusters that link to the [O 18Pb32]28+ layer via BO3 triangles. The presence of [OPb4Mn2Cl2(BO 3)8]16- clusters is associated with large cross-like vacancies in the [O18Pb32]28+ layer.


Turner R.W.,Drey | Siidra O.I.,Saint Petersburg State University | Rumsey M.S.,Natural History Museum in London | Polekhovsky Y.S.,Saint Petersburg State University | And 4 more authors.
Mineralogical Magazine | Year: 2015

Yeomanite, Pb2O(OH)Cl, is a new Pb-oxychloride found in the manganese pod mineral assemblage at Merehead (Torr Works) Quarry, near Cranmore, Somerset, England. Yeomanite is named in joint recognition of Mrs Angela Yeoman (1931-) and her company, Foster Yeoman, who operated Merehead Quarry for aggregate until 2006. The mineral is normally white, occasionally grey, with a white streak and a vitreous to transparent lustre. Invariably intimately associated with mendipite, yeomanite appears to be formed of small, twisted, rope-like fibres growing from the end of columnar mendipite masses, forming loose mats and strands resembling asbestos. Individual fibres are generally <8 mm long, but exceptionally may reach up to 15 mm. There is a perfect cleavage parallel to the long axis of the fibres but this is masked by the fibrous nature, especially as individual fibres break easily. The Dcalc for the ideal formula is 7.303 g/cm3. The mean RI in air at 589 nm is 2.27. The eight strongest reflections in the powder X-ray diffraction pattern [(d in Å) (Intensity) (hkl)] are: 2.880(100)(113); 2.802(78)(006); 3.293(61)(200); 3.770(32)(011); 2.166(22)(206); 1.662(19)(119); 2.050(18)(303); 3.054(17)(105) Yeomanite is orthorhombic, Pnma, a = 6.585(10), b = 3.855(6), c = 17.26(1) Å, V = 438(1) Å3, Z = 4. Yeomanite is a new example of the growing family of lead oxychloride minerals that have a structure based upon oxocentred OPb4 tetrahedra, which, in this mineral, jointly with OHPb3 triangles, form [O(OH)Pb2]+ chains similar to those observed in synthetic Pb2O(OH)I. Yeomanite is structurally related to sidpietersite, penfieldite and laurionite. © 2015 by Walter de Gruyter Berlin/Boston.


Kovrugin V.A.M.,Saint Petersburg State University | Siidra O.I.,Saint Petersburg State University | Zaitsev A.N.N.,Natural History Museum in London | Spratt J.O.,Natural History Museum in London | And 3 more authors.
European Journal of Mineralogy | Year: 2016

Pottsite from the Linka mine (Nevada, USA) was studied by scanning electron microscopy, energy- and wavelengthdispersive analyses, and single-crystal X-ray diffraction. The formula, calculated on the basis of (V + As) = 4, shows that the Pb/Bi atomic ratio in pottsite varies between 0.86 and 1.48, and a plot of Pb vs. Bi (atoms per formula unit) suggests that the 3Pb2+ ↔ 2Bi3+ substitution is operative defining two compositional groups: one with low Pb/Bi atomic ratio (0.86-1.01), the other with high Pb/Bi ratio (1.22-1.48). Structure refinement shows that the crystal studied by X-ray diffraction has a low Pb/Bi ratio. Pottsite crystallizes in the tetragonal space group I41/a, a = 11.0839(5), c = 12.6516(6) Å,V= 1554.29(16) Å3, Z= 1. The crystal structure was solved by direct methods and refined to R1 = 0.040 for 1167 unique reflections with F >4σF. The structure contains one A site split into partially occupied A(1) and A(2) sites. The A(1) site is populated by Pb0.500Bi0.380Ca0.030, whereas A(2) is occupied by Pb0.068Ca0.032, with a site occupation factor (s.o.f) of 0.07. The Bi(1) site has a s.o.f of 0.84 and forms a distorted but symmetrical square antiprismatic coordination environment, which indicates a low degree of stereochemical activity of the lone electron pair on Bi3+. The symmetrically independent V(1) site has a V0.983As0.017 population and is coordinated by four oxygen atoms to form a distorted VO4 tetrahedron. The minor amount of chlorine in pottsite is restricted to the Ow site (O0.928Cl0.072) which belongs to the H2O molecule. The atomic arrangement in the structure of pottsite can be described as the packing of isolated V5+O4 trahedra, linked with heavy cations via common oxygen atoms to form 2D blocks or double-layered (DL) structural units that are parallel to (001). The DL units are formed by pairs of vanadate tetrahedra arranged opposite one to each other and oriented in opposite directions. Water molecules are located in between vanadate tetrahedral groups to form [(VO)4(H2O)]3- chains which are separated from adjacent chains in the (001) plane by rows of Pb2+and Bi3+ cations extending in the [120] direction. Two adjacent DL units are shifted one relative to the other by a translation of ±1/2 unit along the b axis, with an interlayer spacing of about 1.13 A, measured as the shortest distance between adjacent O-O edges of the VO4 tetrahedra. The structure of pottsite is compared to that of related vanadate minerals based on isolated V5+O4 tetrahedra with formation of DL units. The observed variations in Pb and Bi contents and the single-crystal X-ray diffraction data suggest a general formula of pottsite as (Pb3xBi4-2x)(VO4)4·H2O, 0.8 < x < 1.0, and an ideal mineral formula of (Pb3Bi)Bi(VO4)4·H2O. © 2015 E. Schweizerbart'sche Verlagsbuchhandlung.

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