Terlinguacreekite, ideally Hg 2+ 3 O 2 Cl 2 , has a very pronounced subcell that is orthorhombic, space-group choices Imam , Imcm , Ima 2 and I 2 cm , with unit-cell parameters refined from powder data: a 6.737(3), b 25.528(10), c 5.533(2) A, V 951.6(6) A 3 , a:b:c 0.2639:1:0.2167, Z = 8. The true symmetry, supercell unit-cell parameters, and details regarding the crystal structure are unknown. The strongest nine lines of the X-ray powder-diffraction pattern [ d in A ( I )(subcell hkl )] are: 5.413(30)(011), 4.063(80)(121), 3.201(50)(080), 3.023(50)(161), 2.983(60)(240), 2.858(30)(211), 2.765(50)(002), 2.518(100b)(091, 251) and 2.026(30)(242). The mineral is found in an isolated area measuring approximately 1 × 0.5 m in the lower level of the Perry pit, Mariposa mine, Terlingua mining district, Brewster County, Texas (type locality), as mm-sized anhedral dark orange to reddish orange crusts of variable thickness on calcite, and rarely as 0.5 mm-sized aggregates of crystals of the same color. It has also been identified at the McDermitt mine, Humboldt County, Nevada, U.S.A., where it occurs with kleinite and calomel in silicified volcanic rocks and sediments. Terlinguacreekite is a secondary phase, most probably formed from the alteration of primary cinnabar or native mercury. At Terlingua, most crusts are thin, almost cryptocrystalline, with no discernable forms, and are resinous and translucent to opaque. Crystals are up to 0.2 mm in length, subhedral, acicular to prismatic, elongation [001], with a maximum length-to-width ratio of 4:1. They are vitreous, transparent, and some crystals have brightly reflecting faces, which may be {010} and {110}. The streak is yellow, and the mineral is brittle with an uneven fracture, no observable cleavage, and is soft, nonfluorescent under both long- and short-wave ultraviolet light. D (calc.) is 9.899 g/cm 3 (empirical formula). Material from the McDermitt mine is reversibly photosensitive, and turns from vivid orange to black in strong light. In reflected plane-polarized light, it is bluish grey, with very weak (in air) to distinct (in oil) bireflectance, nonpleochroic, and distinctly anisotropic, with colors masked by ubiquitous yellowish orange to orange internal reflections. Measured values of reflectance obtained in air and in oil are tabulated. Averaged results of electron-microprobe analysis give HgO 92.03, Cl 9.54, Br 1.22, sum 102.79, less O = Cl + Br 2.28, total 100.51 wt.%. The empirical formula is Hg 2+ 3.00 O 2.00 (Cl 1.90 Br 0.11 ) ∑2.01 , based on O + Cl + Br = 4 atoms per formula unit. The mineral name recalls the creek that flows through the Terlingua mining district and into the Rio Grande River.

Nevadaite, (Cu2+, square, Al, V3+)(6) (PO4)(8) F-8 (OH)(2) (H2O)(22), is a new supergene mineral species from the Gold Quarry mine, near Carlin, Eureka County, Nevada, U.S.A. Nevadaite forms radiating clusters to 1 mm of prismatic crystals, locally covering surfaces more that 2 cm across; individual crystals are elongate on [001] with a length:width ratio of >10:1 and a maximum diameter of similar to30 mu.m. It also occurs as spherules and druses associated with colorless to purple-black fluellite, colorless wavellite, strengite-variscite, acicular maroon-to-red hewettite, and rare anatase, kazakhstanite, tinticite, leucophosphite, torbernite and tyuyamunite. Nevadaite is pale green to turquoise blue with a pale powder-blue streak and a vitreous luster; it does not fluoresce under ultraviolet light. It has no cleavage, a Mohs hardness of similar to3, is brittle with a conchoidal fracture, and has measured and calculated densities of 2.54 and 2.55 g/cm(3), respectively. Nevadaite is biaxial negative, with alpha 1.540, beta 1.548, gamma 1.553, 2V(obs.) = 76, 2V(calc.) = 76degrees pleochroic with X pale greenish blue, Y very pale greenish blue, Z blue, and with absorption Z much greater than X > Y and orientation X = c, Y = a, Z = b. Nevadaite is orthorhombic, space group P2(1)mn, a 12.123(2), b 18.999(2), c 4.961(1) Angstrom, V 1142.8(2) Angstrom(3), Z = 1, a:b:c = 0.6391:1:0.2611. The strongest seven lines in the X-ray powder-diffraction pattern [d in Angstrom(I)(hkl)] are: 6.077(10)(200), 5.618(9)(130), 9.535(8)(020), 2.983(6)(241), 3.430(4)(041), 2.661(4)(061), and 1.844(4)(352). A chemical analysis with an electron microprobe gave P2O5 32.54, A1(2)O(3) 27.07, V2O3 4.24, Fe2O3 0.07, CuO 9.24, Zn0 0.11, F 9.22, H2O (calc.) 23.48, OH = F -3.88, sum 102.09 wt.%; the valence states of V and Fe, and the amount of H2O, were determined by crystal-structure analysis. The resulting empirical formula on the basis of 63.65 anions (including 21.65 H2O pfu) is (Cu-2.00(2+) Zn0.02V0.983+ Fe-0.01(3+) Al-1.15)(Sigma4.16) Al-8 P-7.90 O-32 [F-8.37 (OH)(1.63)](Sigma10) (H2O)(21.65). The crystal structure 6f nevadaite was solved by direct methods and refined to an R index of 4.0% based on 1307 observed reflections collected on a four-circle diffractometer with MoKalpha X-radiation. The structure consists of ordered layers of vertex-sharing octahedra and tetrahedra alternating with layers of disordered vertex-sharing and face-sharing octahedra in the b direction, [A1phi(5)] chains of octahedra are decorated by. (PO4) tetrahedra that share vertices with octahedra adjacent in the chain. These chains link in the c direction by sharing-vertices between octahedra and tetrahedra to form an ordered layer of the form [Al-8(PO4)(8)F-8(H2O)(8) ]. In the disordered layer, octahedra containing positionally disordered Cu2+ V3+, Al and square (vacancy) share trans faces to form columns that link by sharing octahedron vertices to form ribbons extending in the c direction; the resulting layer has the form {(Cu(2)(2+)square(2)V(3+),Al)(Sigma6) (H2O)(12) (OH)<INFThe layers link in the b direction by sharing vertices between octahedra and tetrahedra. Although decorated chains topologically equivalent to that in nevadaite are common in many oxysalt minerals, its chain is geometrically distinct from those topologically equivalent chains. The M-M linkage along the [Mphi(5)] chains in most minerals take place through trans vertices of the octahedra, with one example of linkage through cis vertices; in nevadaite, the M-M linkage involves both trans and cis vertices, as does the chain in slavikite. In most of these decorated chains, alternate tetrahedra along the chain occur either in a trans or a cis arrangement. In nevadaite and slavikite, the tetrahedra are arranged in both trans and cis arrangements; the arrangements in these, two minerals are geometrically distinct, however.

A new occurrence of the rare mineral species ordonezite has been found at the Theodoso Soto tin mine, near Sapioris, Durango, Mexico. The average composition of the samples is (Zn0.98Fe0.02)(Sigma1.00)Sb2.00O6; the core of the crystals is slightly richer in Fe than the rim. The mineral is uniaxial (+), with all n greater than 2.30 (n(calc) is 2.38 at 589 nm); D-obs 6.66 g/cm(3), D-calc 6.67 g/cm(3). It is isostructural with ferrotapiolite, with a 4.668(2), c 9.269(6) Angstrom (from powder-diffraction data), space group P4(2)/mnm, and is twinned on {103}. Its crystal structure, refined to R = 4.1, wR = 4.3% using 163 observed reflections, is fully cation-ordered.

Kampfite, ideally Ba-6[(Si,Al)O-2](8)(CO3)(2)Cl-2(CI,H2O)(2), is a newly identified mineral species found in barium-silicate-rich deposits at Big Creek and Rush Creek, Fresno County, California. It forms irregular masses up to 10 mm in size enclosed in quartz-rich portions of the sanbornite-bearing rock. It is light blue-grey, with one perfect cleavage on {001}. Other physical properties are: brittle, translucent, nonfluorescent, vitreous luster, white streak, hardness 3, uneven fracture. Kampfite is uniaxial negative, omega 1.642(2), epsilon 1.594(2), nonpleochroic. It is hexagonal, with unit-cell parameters refined from powder data: a 5.244(2), c 29.83(1) Angstrom, V 710.5(4) Angstrom (3), and Z = 1. The strongest seven lines of the X-ray powder-diffraction pattern [d in Angstrom (I)(hkl)] are: 14.67(100)(002),3.883(100)(104),3.357(50)(106), 2.988(60)(00 (1) over bar(0) over bar), 2.887(50)(108),2.616(70)(110), and 1.969(50)(11 (1) over bar(0) over bar). Precession photographs show that possible space-groups are P6(3)/mmc, P (6) over bar 2c, P6(3)mc, P (3) over bar (1)c and P3(1)c. The empirical formula of kampfite (based on the average of three electron-microprobe analyses, normalized on 26 anions) is: (Ba5.83Na0.04Ca0.02)Sigma (5.89) [(Si5.18Al2.36)(Sigma7.54)O-15.08](CO3)(2)Cl-2[(H2O)Cl-0.45]Sigma1.45. The calculated density is 3.51 g/cm(3). All crystals studied contain inclusions or are multiple. Thus, it was not possible to unambiguously determine the correct space-group or precise details of the structure. However, the preliminary results show that the structure is based on double layers of tetrahedra, [T4O8](infinity), consisting of six-membered rings, with three layers of Ba polyhedra connecting the layers of tetrahedra. Kampfite is part of the monteregianite-(Y) - wickenburgite series (Strunz classification) and is structurally and chemically similar to cymrite. The mineral name honors Anthony R. Kampf, Los Angeles County Museum of Natural History, for his many significant contributions to the study of new and rare minerals.

The crystal structure and M-site populations of a series of micas-1M from miarolitic pegmatites that formed within host granitic rocks of the Precambrian, anorogenic Pikes Peak batholith, central Colorado, were determined by single-crystal X-ray diffraction data. Crystals fall in the polylithionite-siderophyllite-annite field, being 0 less than or equal to Li less than or equal to 2.82, 0.90 less than or equal to Fe-total less than or equal to 5.00, 0.26 less than or equal to([6])Al less than or equal to 2.23 apfu. Ordering of trivalent cations (mainly Al3+) is revealed in a cis-octahedral site (M2 or M3), which leads to a lowering of the layer symmetry from C12/m(1) (siderophyllite and annite crystals) to C12(1) diperiodic group (lithian siderophyllite and ferroan polylithionite crystals). On the basis of mean bond length the ordering scheme of octahedral cations is mostly meso-octahedral, whereas the mean electron count at each M site suggests both meso- and hetero-octahedral ordering, the calculated mean atomic numbers being M1 = M3 not equal M2, M2 = M3 not equal M1 and M1 not equal M2 not equal M3. As the siderophyllite content increases, so do the a, b, and c unit-cell parameters, as well as the refractive indices, primarily np. The tetrahedral rotation angle, alpha, is generally small (1.51 less than or equal to alpha less than or equal to 5.04 degrees) and roughly increases with polylithionite content, whereas the basal oxygen out-of-plane tilting, Delta z, is sensitive both to octahedral composition and degree of order (0.0 less than or equal to Delta z less than or equal to 0.009 Angstrom for siderophyllite and annite, 0.058 less than or equal to Delta z less than or equal to 0.144 Angstrom for lithian siderophyllite and ferroan polylithionite crystals).

Afghan Ruby and Sapphire GEMS & GEMOLOGY Summer 2000 he gem mines of Afghanistan are some of the oldest in the world.The lapis lazuli mines at Sar-e-Sang, in the Badakhshan region, have been worked for at least 6,500 years (see, e.g., Wyart et al., 1981).Today, Afghanistan continues to be an important source of various gem minerals-including emerald, ruby, sapphire, aquamarine, tourmaline, and spodumene (see, e.g., Bowersox and Chamberlin, 1995).Yet relatively little is known about many of the gem localities.This article reports on the only known source of ruby in Afghanistan: the Jegdalek region.A historical review, the geology, mining methods, and current production of gem corundum (figure 1) from Jegdalek are given below, together with the results of our research on the gemological properties of this material. BACKGROUNDAlthough most of the records of the Ministry of Mines and Industry have been destroyed by the rocket attacks and bombs that have plagued Kabul since 1979, we were able to glean a fair amount of information from the literature.The geographic location of Afghanistan among several powerful neighbors (i.e., China, Iran, Pakistan, Uzbekistan, Tajikistan, and Turkmenistan; figure 2) has resulted in a long history of turmoil.Additionally, invasions by the Greeks (327 BC), Mongols (1227), British (1838-1919), and Russians (1979-1988), among others, destroyed and/or displaced portions of the Afghan population.However, these major invasions also influenced gem exploration and production, as gems were sought to trade for weapons.In addition, throughout history, Afghan mining areas have been the objects of tribal wars and banditry (see, e.g., Wood, 1841).In 1992, the senior author experienced nightly rocket attacks when he visited the ruby mining area.The Jegdalek mines have been worked for more than 700 years.During the 1200s, wealthy Muhammadan merchants sold rubies to Kublai Khan and other famous historical fig-

The current definition of samarskite-group minerals suggests that ishikawaite is a uranium rich variety of samarskite whereas calciosamarskite is a calcium rich variety of samarskite. Because these minerals are chemically complex, usually completely metamict, and pervasively altered, their crystal chemistry and structure are poorly understood. Warner and Ewing (1993) proposed that samarskite is an A(3+)B(5+)O(4) mineral with an atomic arrangement related to alpha-PbO2. X-ray diffraction analyses of the recrystallized type specimen of ishikawaite and the Ca-rich samarskite reveal that they have the same structure as samarskite-(Y) recrystallized at high temperatures. Electron microprobe analyses show that the only significant difference between samarskite-(Y), ishikawaite, and calciosamarskite lies in the occupancy of the A-site. The A-site of samarskite-(Y) is dominated by Y+REE whereas the A-site of ishikawaite is dominantly U+Th and calciosamarskite is dominantly Ca. Additionally, a comparison of these data to those of Warner and Ewing (1993) show that in several cases Fe2+ or Fe3+ are dominant in the A-site. We propose that the name samarskite-(REE+Y) should be used when one of these elements is dominant and that the mineral be named with the most abundant of these elements as a suffix. The name ishikawaite should be used only when U+Th are dominant and the name calciosamarskite should only be used when Ca is the dominant cation at the A-site. Finally, because of the inability to quantify the valence state of iron in these minerals, the exact nature of the valence state of iron in these minerals could not be determined in this study.

Simmonsite, Na2LiAlF6, a new mineral of pegmatitic-hydrothermal origin, occurs in a late-stage breccia pipe structure that cuts the Zapot amazonite-topaz-zinnwaldite pegmatite located in the Gillis Range, Mineral Co., Nevada, U.S.A. The mineral is intimately intergrown with cryolite, cryolithionite and trace elpasolite. A secondary assemblage of other alumine-fluoride minerals and a second generation of cryolithionite has formed from the primary assemblage. The mineral is monoclinic, P2(1) or P2(1)/m, a = 7.5006(6) Angstrom, b = 7.474(1) Angstrom, c = 7.503(1) Angstrom, beta = 90.847(9)degrees, V = 420.6(1) Angstrom(3), Z = 4. The four strongest diffraction maxima [d (Angstrom), hkl, I/I-100] are (4.33, 111 and 11 (1) over bar, 100); (1.877, 400 and 004, 90); (2.25, 13 (1) over bar, 113, 131 and 311, 70); and (2.65, 220, 202, 022, 60). Simmonsite is pale buff cream with white streak, somewhat greasy, translucent to transparent, Mohs hardness of 2.5-3, no distinct cleavage, subconchoidal fracture, no parting, not extremely brittle, D-m is 3.05(2) g/cm(3), and D-c is 3.06(1) g/cm(3). The mineral is biaxial, very nearly isotropic, N is 1.359(1) for lambda = 589 nm, and birefringence is 0.0009. Electron microprobe analyses gave (wt%) Na = 23.4, Al = 13.9, F = 58.6, Li = 356 (calculated), with a total of 99.46. The empirical formula (based on 6 F atoms) is Na1.98Li1.00Al1.00F6. The crystal structure was not solved, presumably because of unit-cell scale twinning, but similarities to the perovskite-type structure exist.The mineral is named for William B. Simmons, Professor of Mineralogy and Petrology, University of New Orleans, New Orleans.

Pegmatites of the Pala and Mesa Grande Pegmatite Districts, San Diego County, California are typically thin, sheet-like composite pegmatite-aplite dikes. Aplitic portions of many dikes display pronounced mineralogical layering referred to as "line rock," characterized by fine-grained, garnet-rich bands alternating with albite- and quartz-rich bands. Thermal modeling was performed for four dikes in San Diego County including the 1 m thick Himalaya dike, the 2 m thick Mission dike, the 8 m thick George Ashley dike, and the 25 m thick Stewart dike. Calculations were based on conductive cooling equations accounting for latent heat of crystallization, a melt emplacement temperature of 650 degrees C into 150 degrees C fractured, gabbroic country rock at a depth of 5 km, and an estimated 3 wt% initial H2O content in the melt. Cooling to <550 degrees C at the center of each dike occurred in similar to 9 years for the Stewart dike, similar to 340 days fur the George Ashley dike, similar to 22 days for the Mission dike, and similar to 5 days for the Himalaya dike. Based on these calculations, growth rates fur large pegmatitic minerals such as the 10 cm long Himalaya hanging wall tourmaline crystals may have been on the order of 10(-5) cm/s. Crystal size distribution (CSD) studies of garnet from layered aplites suggest growth rates of about 10(-6) cm/s. These results indicate that the dikes cooled and crystallized rapidly, with variable nucleation rates but high overall crystal-growth rates. Initial high nucleation rates coincident with emplacement and strong undercooling can account for the millimeter-size aplite grains. Lower nucleation rates coupled with high growth rates can explain the decimeter-size minerals in the hanging walls, cores, and miarolitic cavities of the pegmatites. The presence of tourmaline and/or lepidolite throughout these dikes suggests that although the melts were initially H2O-undersaturated, high melt concentrations of incompatible (or fluxing) components such as B, F, and Li (+/-H2O), aided in the development of large pegmatitic crystals that grew rapidly in the short times suggested by the conductive cooling models.

Esperanzaite, ideally NaCa2Al2(As5+O4)(2)F-4(OH). 2H(2)O, Z = 2, is a new mineral species from the La Esperanza mine, Durango State, Mexico. The mineral occurs as blue-green botryoidal crystalline masses on rhyolite, with separate spheres up to 1.5 mm in diameter. The Mohs hardness is 4 1/2, and the specific gravity, 3.24 (obs.) and 3.36(3) (calc.). Optical properties were measured in 589 nm light. Esperanzaite is biaxial (-), X = Y = Z = colorless, alpha 1.580(1), beta 1.588(1), and gamma 1.593(1); 2V(obs) is 74(1)degrees and 2V(calc) is 76.3 degrees. The dispersion is medium, r < v, and the optic axes are oriented according to a boolean AND Z = +50.5 degrees, b = Y, c boolean AND X = +35 degrees. The strongest five X-ray-diffraction maxima in the powder pattern [d in Angstrom(I)(hkl)] are: 2.966(100)(13 (1) over bar, 31 (1) over bar, 031), 3.527(90)(220), 2.700(90)(221,002,040), 5.364(80)(001,020) and 4.796(80)(011). Esperanzaite is monoclinic, a 9.687(5), b 10.7379(6), c 5.5523(7) Angstrom, beta 105.32(1)degrees, space group P2(1)/m. The atomic arrangement of esperanzaite was solved by direct methods and Fourier analysis (R = 0.032). The Fundamental Building Block (FBB) is formed of [001] stacks of heteropolyhedral tetramers; the tetramers are formed of two arsenate tetrahedra and two Al octahedra, corner-linked in four-member rings. The FBBs are linked by irregular Na phi(5) and Ca phi(8) polyhedra.

(1998). The Geology, Mineralogy, and History of the Himalaya Mine, Mesa Grande, San Diego County, California. Rocks & Minerals: Vol. 73, No. 3, pp. 156-180.

Abstract The turquoise group has the general formula: A0-1B6(PO4)4-x(PO3OH)x(OH)8‧4H2O, where x = 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 dominant A-site vacancy. Aheylite is established as a new member of the group, and is characterized by having Fe2+ dominant in the A-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 variable A-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, Dm 2.68(2), Dc 2.71, not magnetic, not fluorescent, mean RI about 1.60. a 7.505(2), b 9.723(3), c 7.814(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, Dm 2.84(2), Dc 2.90. a 7.400(1), b 9.896(1), c 7.627(1) Å, α 110.87°, β 115.00°, γ 69.96°, V 460.62(9) Å3, Z = 1.