Brittle Tenacity Research Articles

WERNERBAURITE, , AND SCHINDLERITE, , THE FIRST HYDRONIUM-BEARING DECAVANADATE MINERALS

WERNERBAURITE, , AND SCHINDLERITE, , THE FIRST HYDRONIUM-BEARING DECAVANADATE MINERALS

Cerchiaraite-(Fe) and cerchiaraite-(Al), two new barium cyclosilicate chlorides from Italy and California, USA

AbstractThe ideal formula for members of the cerchiaraite group is Ba4M4(Si4O12)O2(OH)4Cl2[Si2O3(OH)4], where M represents Mn3+, Fe3+ or Al in the octahedral site. A suffix-based naming scheme is used in which the original cerchiaraite is renamed cerchiaraite-(Mn) and two new minerals are named cerchiaraite-(Fe) and cerchiaraite-(Al). The type localities for cerchiaraite-(Fe) are the Cerchiara mine, Liguria, Italy and the Esquire No. 7 and No. 8 claims, Big Creek, Fresno County, California, USA. The type localities for cerchiaraite-(Al) are the Esquire No. 1 claim, Rush Creek, Fresno County, California, USA and the Esquire No. 7 and No. 8 claims noted above. At the Cerchiara mine, cerchiaraite-(Fe) occurs in small fractures and veinlets in a Jurassic ophiolitic sequence. It is of secondary hydrothermal origin and occurs as tan to brown thin prisms and matted fibres. Cerchiaraite(Fe) and cerchiaraite-(Al) from the Esquire No. 1, No. 7 and No. 8 claims occur in parallel-bedded quartz-sanbornite vein assemblages which formed as a result of fluid interaction along the margin of the vein. At the Esquire No. 1, No. 7 and No. 8 claims, both cerchiaraite-(Fe) and cerchiaraite-(Al) occur as subparallel aggregates of blue to bluish green irregular prisms. Both minerals are transparent with a vitreous lustre, Mohs hardness ~4½ , brittle tenacity, irregular fracture and no cleavage. The calculated density of cerchiaraite-(Fe) is 3.710 g cm-3; the measured density of cerchiaraite-(Al) is 3.69(3) g cm-3and the calculated density is 3.643 g cm-3. Cerchiaraite-(Fe) is uniaxial (+), with ω = 1.741(2) and ε = 1.768(2); it is weakly pleochroic and O is colourless and E is yellow. Cerchiaraite-(Al) is uniaxial (-), with ω = 1.695(2) and e = 1.677(2); it is strongly pleochroic and O is colourless and E is blue. Electron-microprobe analyses yielded empirical formulae ranging from (Ba3.82Na0.02Ca0.04)Σ3.88(Fe3+3.42Ti4+0.27Al3+0.25Mn3+0.04Mg0.02)Σ4.00Si5.62O15.47(OH)9.31Cl2.22 (Cerchiara mine) to Ba4.00(Al3+2.40Fe3+1.12Mg0.15Fe2+0.12Mn2+0.06)Σ3.85Si5.78O15.34(OH)8.75Cl2.91 (Esquire No. 1 claim). Cerchiaraite is tetragonal with Z = 2 and crystallizes in space group I4/mmm. The cell parameters for cerchiaraite-(Fe) are a = 14.3554(12), c = 6.0065(5) Å and V = 1237.80(5) Å3; those for cerchiaraite(Al) are a = 14.317(4), c = 6.0037(18) Å and V = 1230.6(6) Å3. In the cerchiaraite-(Fe) structure, SiO4 tetrahedra share corners forming a four-membered Si4O12 ring. The ring is corner-linked to an edgesharing chain of Fe3+ O6 octahedra running parallel to c. A Cl site alternates along c with the Si4 O12 ring. A large channel in the framework contains Ba atoms around its periphery and statistically distributed Si2 O7 silicate dimers and Cl atoms. The strong blue pleochroic colour is attributed to Fe2+ - Fe3+intervalence charge transfer along the octahedral chain.

Nashite, Na3Ca2[(V4+V5+9)O28]*24H2O, a new mineral species from the Yellow Cat Mining District, Utah and the Slick Rock Mining District, Colorado: Crystal structure and descriptive mineralogy

Nashite, Na3Ca2[(V4+V5+9)O28]•24H2O, is a new mineral species from the Little Eva mine, Yellow Cat District, Grand County, Utah, and the St. Jude mine, Slick Rock district, San Miguel County, Colorado, USA. Nashite occurs as blades on a corvusite-montroseite-bearing sandstone block intimately associated with calcite, gypsum, huemulite, pascoite, rossite, and sherwoodite. Nashite is bluish-green, with a light bluish-green streak. The mineral is transparent, with a subadamantine luster. Nashite does not fluoresce in short- or long-wave ultraviolet radiation, and has a hardness ca. 2. Nashite has a brittle tenacity, irregular fracture, and one good cleavage on {010}. Density (calc.) = 2.350 g/cm3 based on the empirical formula and single-crystal cell data, and density (calc.) = 2.343 g/cm3 based on the ideal formula and single-crystal cell data. Nashite is biaxial (–), with α 1.737(3), β 1.762(6), and γ 1.775(3). 2 V meas = 70(2)° and 2 V calc = 71°. Optic orientation is Y = b , X ≈ a . The mineral is pleochroic, with X greenish blue, Y yellowish green, and Z yellow, with X > Y >> Z . Electron probe microanalysis and the crystal structure solution gave the empirical formula (based on O = 52): (Na3.063K0.007)Σ3.070(Ca1.984Sr0.039)Σ2.019[(V4+V5+9)O28]•24(H1.995O). The simplified formula is Na3Ca2[(V4+V5+9)O28] •24H2O. Nashite is monoclinic, P 21/ n , with a 10.0099(3), b 21.8472(7), c 11.1504(7) A, and β 116.584(8)°. The strongest four lines in the diffraction pattern are [ d in A( I )( hkl )]: 9.044(100)(111, 101), 8.350(64)(110), 10.995(46)(020), and 2.9942(29)(331, 332, 303, 071, 310). The atomic arrangement of nashite was solved and refined to R1 = 0.0293. The structural unit in nashite is a partially-reduced decavanadate group, with a composition of [(V4+V5+9)O28]7–; charge balance in the structure is maintained by the [Na3Ca2(OH2)22•2H2O]7+ interstitial unit. The interstitial unit consists of chains of Na1 and Na2 octahedra and an irregular CaO2(OH2)6 polyhedron. The chains are linked to the structural unit by direct bonding to oxygen atoms of the [(V4+V5+9)O28]7– group and extensive hydrogen bonding between the H2O molecules of the interstitial group and the oxygen atoms of the structural unit. The mineral is named for Dr. Barbara P. Nash (b. 1944), Professor of Geology and Geophysics at the University of Utah.

Calciodelrioite, Ca(VO3)2(H2O)4, the Ca analogue of delrioite, Sr(VO3)2(H2O)4

AbstractCalciodelrioite, ideally Ca(VO3)2(H2O)4, is a new mineral (IMA 2012-031) from the uraniumvanadium deposits of the eastern Colorado Plateau in the USA. The type locality is the West Sunday mine, Slick Rock district, San Miguel County, Colorado. The new mineral occurs on fracture surfaces in corvusite- and montroseite-impregnated sandstone and forms as a result of the oxidative alteration of these phases. At the West Sunday mine, calciodelrioite is associated with celestine, gypsum, huemulite, metarossite, pascoite and rossite. The mineral occurs as transparent colourless needles, bundles of tan to brown needles and star bursts of nearly black broad blades composed of tightly intergrown needles. Crystals are elongate and striated parallel to [100], exhibiting the prismatic forms {001} and {011} and having terminations possibly composed of the forms {100} and {61}. The mineral is transparent and has a white streak, subadamantine lustre, Mohs hardness of about 2½, brittle tenacity, irregular to splintery fracture, one perfect cleavage on {001} and possibly one or more additional cleavages parallel to [100]. Calciodelrioite is soluble in water. The calculated density is 2.451 g cm– 3. It is optically biaxial (+) with α = 1.733(3), β = 1.775(3), γ = 1.825(3) (white light), 2Vmeas = 87.3(9)° and 2Vcalc = 87°. The optical orientation is X = b; Z ≈ a. No pleochroism was observed. Electronmicroprobe analyses of two calciodelrioite samples and type delrioite provided the empirical formulae (Ca0.88Sr0.07Na0.04K0.01)Σ1.00(V1.00O3)2(H2.01O)4, (Ca0.76Sr0.21Na0.01)Σ0.98(V1.00O3)2(H2.01O)4 and (Sr0.67Ca0.32)Σ0.99(V1.00O3)2(H2.00O)4, respectively. Calciodelrioite is monoclinic, I2/a, with unit-cell parameters a = 14.6389(10), b = 6.9591(4), c = 17.052(2) Å, β = 102.568(9)°, V = 1695.5(3) Å3 and Z = 8. The seven strongest lines in the X-ray powder diffraction pattern [listed as dobs Å (I)(hkl)] are as follows: 6.450(100)(011); 4.350(16)(013); 3.489(18)(020); 3.215(17)(022); 3.027(50)(multiple); 2.560(28)(15,413); 1.786(18)(028). In the structure of calciodelrioite (refined to R1 = 3.14% for 1216 Fo > 4σF), V5+O5 polyhedra link by sharing edges to form a zigzag divanadate [VO3] chain along a, similar to that in the structure of rossite. The chains are linked via bonds to Ca atoms, which also bond to H2O groups, yielding CaO3(H2O)6 polyhedra. The Ca polyhedra form a chain along b. Each of the two symmetrically independent VO5 polyhedra has two short vanadyl bonds and three long equatorial bonds. Calciodelrioite and delrioite are isostructural and are the endmembers of the series Ca(VO3)2(H2O)4–Sr(VO3)2(H2O)4. Calciodelrioite is dimorphous with rossite, which has a similar structure; however, the smaller 8-coordinate Ca site in rossite does not accommodate Sr.

CORDYLITE-(La), A NEW MINERAL SPECIES IN FENITE FROM THE BIRAYA Fe-REE DEPOSIT, IRKUTSK, RUSSIA

Cordylite-(La), (Na,Ca)2Ba2(La3Sr)∑4(CO3)8F2, is a new mineral species (IMA2010–058) from the Biraya Fe–REE deposit, Irkutsk district, Russia. It occurs in direct association with barite, biraite-(Ce), niobium-rich chevkinite-(Ce), fergusonite-(Nd), ancylite-(Ce) and ancylite-(La), daqingshanite-(Ce) and daqingshanite-(La), bastnasite-(Ce), hydroxylbastnasite-(Ce), carbocernaite, monazite-(Ce), talc, humite, thorite, pyrite, and pyrrhotite in carbonate veins composed of aragonite, strontianite, calcite, dolomite, and cordylite-(Ce). Cordylite-(La) forms as colorless, honey-yellow, or pinkish yellow, irregularly-shaped, tabular, or short-prismatic hexagonal crystals up to about 3 mm across. The only forms observed are {1010} and {0001} and crystals have perfect cleavage on {0001}. Crystals have a greasy to vitreous luster, a brittle tenacity, a conchoidal to uneven fracture, and a hardness of 4 on the Mohs scale. Crystals are uniaxial (−), ɛ = 1.573–1.574, and ω = 1.749–1.751. The empirical formula for two different crystals gave: (Na1.24Ca0.78)∑2.02Ba2.10[(La1.54Ce1.31Nd0.17Pr0.04)∑3.06Sr0.89]∑3.95(C1.01O3)8(F1.78OH0.05)∑1.83 and(Na1.23Ca0.79)∑2.02Ba1.98[(La1.43Ce1.33Nd0.25Pr0.10)∑3.11Sr0.94]∑4.05(C1.01O3)8(F1.51OH0.38)∑1.89. The crystal structure, solved on the same two crystals ( R 1 = 0.0246 and 0.0205) gave the unit cell parameters in P 63/ mcc: a = 5.1182(5) and c = 23.1785(16) A and V = 525.84(16) A3 and a = 5.1196(3) and c = 23.1784(16) A and V = 525.13(5) A3 with Z = 1, and confirms that the mineral is isostructural with cordylite-(Ce). We also discuss new heterovalent substitution mechanisms found in the cordylite group minerals and the effect they have during the formation of crystals.

Alcaparrosaite, K3Ti4+Fe3+(SO4)4O(H2O)2, a new hydrophobic Ti4+ sulfate from Alcaparrosa, Chile

AbstractAlcaparrosaite, ideally K3Ti4+Fe3+(SO4)4O(H2O)2, is a new mineral from the Alcaparrosa mine, Cerritos Bayos, El Loa Province, Antofagasta, Chile (IMA2011-024). The mineral occurs on and intergrown with coquimbite, and is also associated with ferrinatrite, krausite, pertlikite, pyrite, tamarugite and voltaite. It is a relatively early phase which forms during the oxidation of pyritic masses under increasingly arid conditions. Alcaparrosaite crystallizes from hyperacidic solutions in a chemical environment that is consistent with its association with coquimbite. It occurs as pale yellow blades and tapering prisms up to 4 mm in length, flattened on {010} and elongated along [100]. The observed crystal forms are {010}, {110}, {1.13.0} and {021}. The mineral is transparent and has a white streak, vitreous lustre, Mohs hardness of about 4, brittle tenacity, conchoidal fracture and no cleavage. The measured and calculated densities are 2.80(3) and 2.807 g cm–3, respectively. It is optically biaxial (+) with α = 1.643(1), β = 1.655(1), γ = 1.680(1) (white light), 2Vmeas = 70(2)° and 2Vcalc = 70.3°. The mineral exhibits strong parallel dispersion, r < v. The optical orientation is X = b; Y^c = 27° in the obtuse angle β. No pleochroism was observed. Electron-microprobe analyses (average of 4) provided: Na2O 0.32, K2O 20.44, Fe2O3 11.58, TiO2 11.77, P2O50.55, SO347.52, H2O 5.79 (calc); total 97.97 wt.%. The empirical formula (based on 19 O) is (K2.89Na0.07)Σ2.96Ti0.984+Fe0.973+(S0.99P0.01O4)4O0.72(OH)0.28(H2O)2. The mineral is hydrophobic, insoluble in cold and hot water, very slowly soluble in acids and decomposes slowly in bases. Alcaparrosaite is monoclinic, C2/c, with the cell parameters a = 7.55943(14), b = 16.7923(3), c = 12.1783(9) Å, β = 94.076(7)°, V = 1542.01(12) Å3 and Z = 4. The eight strongest lines in the X-ray powder diffraction pattern [dobs in A ˚ (Irel) (hkl)] are 6.907 (41) (021,110); 3.628 (34) (023,13); 3.320 (32) (02); 3.096 (100) (202,33,150); 3.000 (40) (51); 2.704 (38) (23,152); 1.9283 (30) (55); 1.8406 (31) (53,06). In the structure of alcaparrosaite (R1 = 2.57% for 1725 Fo > 4σF), Ti4+ and Fe3+, in roughly equal amounts, occupy the same octahedrally coordinated site. Octahedra are linked into dimers by corner sharing. The SO4 tetrahedra link the dimers into chains parallel to [001] and link the chains into undulating sheets parallel to {010}. The sheets link via 10- and 11-coordinated K atoms in the interlayer region. The structure shares some features with that of goldichite.

POSTITE, Mg(H2O)6Al2(OH)2(H2O)8(V10O28){middle dot}13H2O, A NEW MINERAL SPECIES FROM THE LA SAL MINING DISTRICT, UTAH: CRYSTAL STRUCTURE AND DESCRIPTIVE MINERALOGY

Postite, Mg(H 2 O) 6 Al 2 (OH) 2 (H 2 O) 8 (V 10 O 28 )·13H 2 O, is a new mineral species from the Vanadium Queen mine, La Sal Creek Canyon, and the Blue Cap mine, Lyon Canyon Creek, San Juan County, Utah, U.S.A. Postite occurs as very thin, needle-like prisms with pyramidal terminations; crystals commonly occur in parallel bundles and grow in divergent and “jackstraw” masses. Individual crystals are up to 1 mm long and 50 μm in diameter, and are golden-yellow with a yellow streak. The mineral is transparent, with a subadamantine luster; it does not fluoresce in short- or long-wave ultraviolet radiation. Postite has a Mohs hardness of approximately 2 and brittle tenacity. The mineral has one good cleavage on {001} and at least two perfect cleavages parallel to [001], possibly {100} and {010}. The fracture is splintery. The density calculated from the empirical formula using the single-crystal cell data is 2.226 g/cm 3 . Postite is biaxial (+) with a 2 V angle of 71o. Indices of refraction for postite are α 1.727(3), β 1.733(3), and γ1.745(3). The optical orientation is X = c , Y = b , Z = a . Dispersion was not observed and pleochroism was not perceptible. Electron probe microanalysis and the crystal structure solution gave the empirical formula (Mg 0.97 Na 0.06 Ca 0.04 Sr 0.01 K 0.01 ) ∑1.09 Al 1.94 [(OH) 1.92 (H 2 O) 0.08 ] ‡”2.00 (V 10 O 28 )·27H 2 O. The simplified structural formula of postite is Mg(H 2 O) 6 Al 2 (OH) 2 (H 2 O) 8 (V 10 O 28 ) ·13H 2 O. Postite is orthorhombic, Pccn , with a 16.3357(6), b 24.2434(17), c 11.7343(4) A, V 4647.2(4) A 3 , and Z = 4. The strongest four lines in the diffraction pattern are [ d in A(I)( hkl )]: 8.937(100)(111), 12.190(90)(020), 3.771(24)(113), and 8.248(22)(200). The atomic arrangement of postite was solved and refined to R 1 = 0.0358. The structural unit is a decavanadate polyanion, [V 10 O 28 ] 6− ; charge balance in the structure is maintained by the [Mg(H 2 O) 6 Al 2 (OH) 2 (H 2 O) 8 ·13 H 2 O] 6+ interstitial unit. The interstitial unit consists of a [Mg(H 2 O) 6 ] 2+ monomer, an [Al 2 (OH) 2 (H 2 O) 8 ] 4+ edge-sharing dimer, and thirteen additional H 2 O molecules. The linkage between the structural unit and the interstitial unit results from hydrogen bonding between oxygen atoms of the structural unit with hydrogen atoms of the [Al 2 (OH) 2 (H 2 O) 8 ] 4+ edge-sharing dimer and those of isolated H 2 O molecules. The new mineral is named in honor of Dr. Jeffrey E. Post (b. 1954), Curator-in-Charge of the National Gem and Mineral Collection, U. S. National Museum of Natural History (Smithsonian Institution).

GUNTERITE, Na4(H2O)16(H2V10O28){middle dot}6H2O, A NEW MINERAL SPECIES WITH A DOUBLY-PROTONATED DECAVANADATE POLYANION: CRYSTAL STRUCTURE AND DESCRIPTIVE MINERALOGY

Gunterite, Na 4 (H 2 O) 16 (H 2 V 10 O 28 )·6H 2 O, is a new mineral species from the West Sunday mine, Slick Rock district, San Miguel County, Colorado, U.S.A. Crystals of gunterite are tabular on {001} and generally stacked into elongate curved multiple crystals up to 0.5 mm in maximum dimension; the crystals are orange-yellow, with a yellow streak. The mineral displays a subadamantine luster, and is transparent; it does not fluoresce in short- or long-range ultraviolet radiation. Gunterite has a hardness of about 1, a brittle tenacity, and an irregular fracture; no cleavage or parting was observed. The density calculated from the empirical formula using the single-crystal cell data is 2.398 g cm −3 . Gunterite is biaxial (+), with α 1.735(5), β 1.770(5) and γ 1.825(5); 2 V is equal to 78° (white light). The dispersion v is strong and parallel. Optical orientation; X = b , Y ≈ c ; pleochroism: X yellow, Y orange, Z yellow; Y > X > Z . Gunterite is soluble in water at room temperature. Electronprobe microanalysis and the crystal-structure solution provided the empirical formula (V + Al = 10 apfu ): (Na 3.20 K 0.02 Ca 0.87 ) ∑4.09 [H 1.06 (V 9.99 Al 0.01 ) ∑10 O 28 ]·22H 2 O. The simplified formula of gunterite is Na 4 (H 2 O) 16 (H 2 V 10 O 28 )·6H 2 O. There is extensive substitution of Ca for Na in gunterite, yielding a structural formula of (Na 4− x Ca x ) ∑4.00 (H 2 O) 16 (H 2− x V 10 O 28 )·6H 2 O; the average value of x from the chemical analyses is 0.85. Gunterite is monoclinic, C 2/ m , with a 19.848(2), b 10.1889(11), c 13.1184(15) A, β 130.187(9)°, V 2026.6(4) A 3 , and Z = 2. The strongest four lines in the diffraction pattern [ d in A(I) hkl ] are: 10.01(100)201,001, 8.44(72)110, 8.09(46)111, and 2.997(29)331,401. The atomic arrangement of gunterite was refined to R 1 = 0.0632. The structural unit is a doubly-protonated decavanadate polyanion, {H 2 [V 10 O 28 ]}. The interstitial units linking the structural units contain two Na polyhedra; the Na2 polyhedron is split into two partially occupied sites that are 0.76 A apart, and significant Ca occupies that site. Several of the H 2 O molecules in the interstitial complex are disordered. The mineral is named in honor of Mickey E. Gunter, Professor of Mineralogy at the University of Idaho.

RAKOVANITE, Na3 {middle dot}15H2O, A NEW MEMBER OF THE PASCOITE FAMILY WITH A PROTONATED DECAVANADATE POLYANION

Rakovanite, Na 3 {H 3 [V 10 O 28 ]}·15H 2 O, is a new mineral species from the Sunday and the West Sunday mines, Slick Rock district, San Miguel County, Colorado, USA; the mineral is the natural analog of the previously synthesized phase. Rakovanite is orange, with an orange-yellow streak. Crystals of rakovanite are up to 1 mm in maximum dimension and vary in habit from blocky to prismatic on [100]. The mineral is transparent, with a subadamantine luster; it does not fluoresce in long- or short-wave ultraviolet radiation. Rakovanite displays brittle tenacity, and has a Mohs hardness of 1. No cleavage or parting was observed, and the mineral displays a conchoidal fracture. The density calculated from the ideal formula and the single-crystal cell data is 2.407 g cm −3 . Rakovanite is biaxial (+), with α 589nm = 1.776(5), β 589nm = 1.803(5), γ 589nm = 1.910(6). The measured values of 2 V are: 2 Vz 540nm = 58(1); 2 Vz 589nm = 56(1); 2 Vz 650nm = 53(1)°. Dispersion is r v , strong, parallel; orientation: X = b ; Z c = 8 ° in obtuse β. The pleochroic scheme in rakovanite is: X light yellow, Y orangish yellow, Z yellowish orange, Z > Y > X . Its chemical composition was obtained by electron-probe microanalysis and the crystal-structure refinement; the empirical formula (V = 10 apfu ) is (Na 2.90 K 0.07 Ca 0.01 Al 0.01 ) ∑2.99 {H 2.98 [V 10 O 28 ]}·15H 2 O, and the simplified formula is Na 3 {H 3 [V 10 O 28 ]}·15H 2 O. Rakovanite is monoclinic, space group P 2 1 / n , with a 12.0248(17), b 17.121(3), c 18.140(3) A, β 106.242(8)°, and Z = 4; the strongest four lines in the powder-diffraction pattern [ d in A(I)( hkl )] are: 11.270(100)(101), 7.696(81)(021), 8.709(78)(002), and 6.892(63)(120). The atomic arrangement of rakovanite has been refined to R 1 = 0.0383; the structural unit in the phase is formed of a triply-protonated decavanadate polyanion, {H 3 [V 10 O 28 ]}. The structural units are linked by the interstitial complexes, the (Na 3 ·15H 2 O) contents of which balance the +3 charges of the decavanadate polyanion with a NaO 4 (H 2 O) 2 group, a Na 2 (H 2 O) 10 dimer, and three H 2 O molecules that do not bond to the interstitial cations.

Lead-tellurium oxysalts from Otto Mountain near Baker, California: V. Timroseite, Pb2Cu52+(Te6+O6)2(OH)2, and paratimroseite, Pb2Cu42+(Te6+O6)2(H2O)2, two new tellurates with Te-Cu polyhedral sheets

Timroseite, Pb_2Cu_5^(2+)(Te^(6+)O_6)_2(OH)_2, and paratimroseite, Pb_2Cu_4^(2+)(Te^(6+)O_6)_2(H_2O)_2, are two new tellurates from Otto Mountain near Baker, California. Timroseite is named in honor of Timothy (Tim) P. Rose and paratimroseite is named for its relationship to timroseite. Both new minerals occur on fracture surfaces and in small vugs in brecciated quartz veins. Timroseite is directly associated with acanthite, cerussite, bromine-rich chlorargyrite, chrysocolla, gold, housleyite, iodargyrite, khinite-4O, markcooperite, ottoite, paratimroseite, thorneite, vauquelinite, and wulfenite. Paratimroseite is directly associated with calcite, cerussite, housleyite, khinite-4O, markcooperite, and timroseite. Timroseite is orthorhombic, space group P2_1nm, a = 5.2000(2), b = 9.6225(4), c = 11.5340(5) A, V = 577.13(4) A^3, and Z = 2. Paratimroseite is orthorhombic, space group P2_12_12_1, a = 5.1943(4), b = 9.6198(10), c = 11.6746(11) A, V = 583.35(9) A^3, and Z = 2. Timroseite commonly occurs as olive to lime green, irregular, rounded masses and rarely in crystals as dark olive green, equant rhombs, and diamond-shaped plates in subparallel sheaf-like aggregates. It has a very pale yellowish green streak, dull to adamantine luster, a hardness of about 2 1/2 (Mohs), brittle tenacity, irregular fracture, no cleavage, and a calculated density of 6.981 g/cm^3. Paratimroseite occurs as vibrant neon green blades typically intergrown in irregular clusters and as lime green botryoids. It has a very pale green streak, dull to adamantine luster, a hardness of about 3 (Mohs), brittle tenacity, irregular fracture, good {001} cleavage, and a calculated density of 6.556 g/cm^3. Timroseite is biaxial (+) with a large 2V, indices of refraction > 2, orientation X = b, Y = a, Z = c and pleochroism: X = greenish yellow, Y = yellowish green, Z = dark green (Z > Y > X). Paratimroseite is biaxial (–) with a large 2V, indices of refraction > 2, orientation X = c, Y = b, Z = a and pleochroism: X = light green, Y = green, Z = green (Y = Z >> X). Electron microprobe analysis of timroseite provided PbO 35.85, CuO 29.57, TeO_3 27.75, Cl 0.04, H_2O 1.38 (structure), O≡Cl –0.01, total 94.58 wt%; the empirical formula (based on O+Cl = 14) is Pb_(2.07) Cu^(2+)_(4.80)Te^(6+)_(2.04)O_(12)(OH)_(1.98)Cl_(0.02). Electron microprobe analysis of paratimroseite provided PbO 36.11, CuO 26.27, TeO_3 29.80, Cl 0.04, H_2O 3.01 (structure), O≡Cl –0.01, total 95.22 wt%; the empirical formula (based on O+Cl = 14) is Pb_(1.94)Cu^(2+)_(3.96)Te^(6+)_(2.03)O_(12)(H_2O)_(1.99)Cl_(0.01). The strongest powder X-ray diffraction lines for timroseite are [d_(obs) in A (hkl) I]: 3.693 (022) 43, 3.578 (112) 44, 3.008 (023) 84, 2.950 (113) 88, 2.732 (130) 100, 1.785 (multiple) 33, 1.475 (332) 36; and for paratimroseite 4.771 (101) 76, 4.463 (021) 32, 3.544 (120) 44, 3.029 (023,122) 100, 2.973 (113) 48, 2.665 (131) 41, 2.469 (114) 40, 2.246 (221) 34. The crystal structures of timroseite (R_1 = 0.029) and paratimroseite (R_1 = 0.039) are very closely related. The structures are based upon edge- and corner-sharing sheets of Te and Cu polyhedra parallel to (001) and the sheets in both structures are identical in topology and virtually identical in geometry. In timroseite, the sheets are joined to one another along c by sharing the apical O atoms of Cu octahedra, as well as by sharing edges and corners with an additional CuO_5 square pyramid located between the sheets. The sheets in paratimroseite are joined only via Pb-O and H bonds.

ZINCOSPIROFFITE, A NEW TELLURITE MINERAL SPECIES FROM THE ZHONGSHANGOU GOLD DEPOSIT, HEBEI PROVINCE, PEOPLE'S REPUBLIC OF CHINA

Zincospiroffite (Zn2Te3O8), a new tellurite mineral species, was discovered in the Zhongshangou gold deposit in Chongli County, Hebei Province, China. Since it has only been found as crystallite aggregates of hundreds to thousands of micrometers square in a single polished block, most work on the mineral had been carried out under the microscope. This mineral is intimately associated with calaverite and sphalerite, either as micrometric films coating calaverite or in irregular aggregates replacing calaverite. It is a product of secondary co-oxidation of calaverite, associated with sphalerite, pyrite, and other sulfides. It is a gray and translucent mineral, with a dark green streak and a vitreous luster, without internal reflections, and with a weak anisotropy, bireflectance and pleochroism. It is quite soft, has a brittle tenacity and an uneven fracture. Raman spectroscopy demonstrates that the mineral is a natural analogue of synthetic Zn2Te3O8. An electron-microprobe analysis gave the following composition: ZnO 24.57, PbO 1.64, MgO 0.24, TeO2 71.90, minor FeO and SeO2, total 98.89 (in wt.%), corresponding to an empirical formula (Zn1.97Pb0.05Mg0.04Fe0.02)∑ 2.08 (Te2.95Se0.01)∑2.96O8.00 or, ideally, Zn2Te3O8. Powder X-ray diffraction gave only seven lines with weak intensities [ d in A(I)( hkl ): 4.758(w)(110), 3.240(w)(311), 2.928(m)(113), 2.820(w)(204), 2.155(w)(023,511), 1.985(w)(223), 1.599(w)(425), which are similar to those of the synthetic Zn 2Te3O8 (PDF 44–0241). On the basis of the diffraction pattern, the following unit-cell parameters were obtained: a 12.72(4), b 5.15(1), c 11.82(3) (A), β 99.2(3)°, V 764.57(2.52) A3, with Z = 4 and Dcalc = 5.57 g cm−3. With these parameters, a comparison is made of zincospiroffite, synthetic Zn2Te3O8 and spiroffite. The new mineral and its name were approved by the Commission on New Mineral and Mineral Names of International Mineralogical Association (IMA 2002–047). The only polished section was housed under catalogue number M10442 in the collection of the Geological Museum of China.

A reexamination of the turquoise group: the mineral aheylite, planerite (redefined), turquoise and coeruleolactite

AbstractThe turquoise group has the general formula:A0–1B6(PO4)4−x(PO3OH)x(OH)8.4H2O, wherex= 0–2, and consists of six members: planerite, turquoise, faustite, aheylite, chalcosiderite and an unnamed Fe2+-Fe3+analogue. The existence of ‘coeruleolactite’ is doubtful. Planerite is revalidated as a species and is characterized by a dominantA-site vacancy. Aheylite is established as a new member of the group, and is characterized by having Fe2+dominant in theA-site.Chemical analyses of 15 pure samples of microcrystalline planerite, turquoise, and aheylite show that a maximum of two of the (PO4) groups are protonated (PO3OH) in planerite. Complete solid solution exists between planerite and turquoise. Other members of the group show variableA-site vacancy as well. Most samples of ‘turquoise’ are cation-deficient or are planerite. Direct determination of water indicates that there are 4 molecules of water.Planerite, ideally ☐Al6(PO4)2(PO3OH)2(OH)8.4H2O, is white, pale blue or pale green, and occurs as mamillary, botryoidal crusts as much as several mm thick; may also be massive; microcrystalline, crystals typically 2–4 micrometres, luster chalky to earthy, H. 5, somewhat brittle, no cleavage observed, splintery fracture, Dm2.68(2), Dc2.71, not magnetic, not fluorescent, mean RI about 1.60.a7.505(2),b9.723(3),c7.814(2) Å, α 111.43°, β 115.56°, γ 68.69°, V 464.2(1) Å3, Z = 1.Aheylite, ideally Fe2+Al6(PO4)4(OH)8.4H2O, is pale blue or green, and occurs as isolated and aggregate clumps of hemispherical or spherical, radiating to interlocked masses of crystals that average 3 micrometres in maximum dimension; porcelaneous-subvitreous luster, moderate to brittle tenacity, no cleavage observed, hackly to splintery fracture, not magnetic, not fluorescent, biax. (+), mean RI is about 1.63, Dm2.84(2), Dc2.90.a7.400(1),b9.896(1),c7.627(1) Å, α 110.87°, β 115.00°, γ 69.96°, V 460.62(9) Å3, Z = 1.