Yassir A. Abdu

• Ph.D.
• Professor (Associate) at University of Sharjah

The crystal structures of orthopyroxene (En 86.3 Fs 8.6 Wo 5.1 , space group Pbca ) and pigeonite (En 81.7 Fs 8.8 Wo 9.5 , space group P 2 1 /c ) from the Almahata Sitta ureilite (fragment#051) have been refined to R 1 indices of 3.10% and 2.53%, respectively, using single‐crystal X‐ray diffraction data. The unit formulas were calculated from elect...

Uvite, CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH), is a new mineral of the tourmaline supergroup. It occurs in the Facciatoia quarry, San Piero in Campo, Elba Island, Italy (42°45′04.55″N, 10°12′50.89″E) at the centre of a narrow (2–3 cm wide) vein composed of aggregates of dark brown to black tourmaline, penetrating (magnesite + dolomite)-rich hydrotherm...

Kapoeta is an achondrite meteorite containing mm-sized carbonaceous-chondrite inclusions that are thought to have been incorporated into its parent body by carbonaceous-chondrite impactors (mainly CM “Mighei-type” material). Two different samples (A and B) of the Kapoeta carbonaceous-chondrite materials are studied by Mössbauer spectroscopy at room...

Nanodiamonds, found in a carbonaceous-chondrite material from the gas-rich meteorite Kapoeta, have been studied by micro-Raman spectroscopy. The Raman spectra of these nanodiamonds show the first-order Raman peak of diamond at 1333 cm⁻¹, along with the “D” and “G” peaks of graphitic/amorphous carbon phases(s). The spectra also show additional Raman...

In this paper, we report a one-pot chemical synthesis technique for the preparation of iron and iron-carbide nanoparticles. Mössbauer spectroscopy, X-ray diffraction and magnetometry were used as the main tools to identify the different phases of Fe–C present. The influence of experimental parameters on the structural and compositional properties o...

Micas are among the most commonly-dated minerals by the ⁴⁰Ar/³⁹Ar technique to determine the crystallization or cooling ages of rocks. Interpretation of the geological significance of these ages is largely dependent on understanding how ⁴⁰Ar* (radiogenic argon) can be retained or released from the mineral during the thermal history of a terrane. Th...

Four Ca-rich clinopyroxene samples (3 terrestrial clinopyroxenes and a druse clinopyroxene from the D’Orbigny meteorite) have been studied by near-infrared (NIR) spectroscopy and X-ray structure refinement in order to address the issue of anomalous type-B NIR spectra seen in some terrestrial and extraterrestrial Ca-rich clinopyroxenes. The D’Orbign...

Tamboite (x ¼ 3; y ¼ 2) and metatamboite (x ¼ 3; y ¼ 0), Fe 3þ 3 (SO 4)(Te 4þ O 3) 3 (Te 4þ O(OH) 2)(OH)(H 2 O) x {H 2 O} y , are new tellurite minerals from the Tambo mine, Coquimbo Province, Chile. The two minerals transform to each other reversibly with changes in ambient humidity. They occur as pale-yellow clusters of radiating fiber bundles on...

The mechanical behavior of carbonate-bearing fluorapatite (CFAP) (with up to 5.5 wt% CO3) was investigated at high pressure up to 7 GPa. The incorporation of carbonate in CFAP samples was investigated by FTIR spectroscopy. The chemical formulae and cell parameters are Ca4.90Fe0.04 (PO4)2.87 (CO3)0.13 F1.23 and a = 9.3527(1), c = 6.8752(1) Å, V = 52...

In this work we report on a complete crystal-chemical characterization of a near end-member riebeckite from Malawi, and use the available data to critically compare information obtained from different analytical methods. The sample occurs as well-formed and very large single crystals in pegmatitic rocks. Accurate site-populations were determined by...

Brandãoite, [BeAl2(PO4)2(OH)2(H2O)4](H2O), a new Be-Al-phosphate mineral from the João Firmino mine, Pomarolli farm region, Divino das Laranjeiras county, Minas Gerais State, Brazil: description and crystal structure - L. A. D. Menezes Filho, M. L. S. C. Chaves, M. A. Cooper, N. A. Ball, Y. A. Abdu, R. Sharpe, M. C. Day, F. C. Hawthorne

Beusite-(Ca), ideally Ca²⁺2(PO4)2, is a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada. It occurs in a beryl-columbite-phosphate rare-element pegmatite where it is commonly intergrown with triphylite-lithiophilite or sarcopside, and may form by exsolution from a high-temperature (Li,Ca)-rich grafton...

Graftonite-(Mn), ideally M1MnM2,M3Fe2(PO4)2, and graftonite-(Ca), ideally M1CaM2,M3Fe2(PO4)2, two new minerals of the graftonite group from Poland - Adam Pieczka, Frank C. Hawthorne, Neil Ball, Yassir Abdu, Bożena Gołębiowska, Adam Włodek, Jan Żukrowski

We report the finding of nanodiamonds, coexisting with amorphous carbon, in carbonaceous-chondrite (CC) material from the Kapoeta achondritic meteorite by Fourier-transform infrared (FTIR) spectroscopy and micro-Raman spectroscopy. In the C-H stretching region (3100-2600 cm −1), the FTIR spectrum of the Kapoeta CC material (KBr pellet) shows bands...

High-temperature X-ray powder-diffraction study of astrophyllite, K2NaFe72+Ti2(Si4O12)2O2(OH)4F, and investigation of the samples annealed at 600 and 700 °C, reveal the occurrence of a phase transformation due to the thermal iron oxidation coupled with (1) deprotonation according to the scheme Fe2+ + OH− → Fe3+ + O2− + ½H2 ↑, and (2) defluorination...

Olivinites, together with olivine megacrysts, are the most magnesian phases found in angrites. Their chemical composition (mg# 90) is out of equilibrium with the groundmass and far away from that of possible precipitates from angrite parent melts. Therefore olivinites, as well as olivine megacrysts, were considered as xenoliths and xenocrysts. We r...

The chemical composition and chemical formula for ferro-ferri-nybøite given by Lussier et al. (2014) are wrong due to incorporation of errors during preparation of the paper. The data given in the original IMA submission are correct and are given here: SiO2 47.06, TiO2 0.50, Al2O3 3.16, Fe2O3 12.43, FeO 22.37, (Fetot=33.56), MnO 2.18, ZnO 0.06, MgO...

The chemical composition and chemical formula for ferro-ferri-nybøite given by Lussier et al. (2014) are wrong due to incorporation of errors during preparation of the paper. The data given in the original IMA submission are correct and are given here:

Fogoite-(Y), Na3Ca2Y2Ti(Si2O7)2OF3, is a new mineral from the Lagoa do Fogo, São Miguel Island, the Azores. It occurs in cavities as highly elongated (on [001]) prisms, up to 2000 μm long and 50 μm × 50 μm in cross-section, associated with sanidine, astrophyllite, fluornatropyrochlore, ferrokentbrooksite, quartz and ferro-katophorite. Crystals are...

We report an experimental study of the intracrystalline distribution of Fe²⁺ and Mg between the non-equivalent octahedral sites, M1 and M2, in orthopyroxene from the Kapoeta meteorite by single-crystal X-ray diffraction and Mössbauer spectroscopy. The Fe²⁺-Mg ordering closure temperatures obtained by X-ray structure refinement for two orthopyroxene...

We report an experimental study of the intracrystalline distribution of Fe 2+ and Mg between the non-equivalent octahedral sites, M1 and M2, in orthopyroxene from the Kapoeta meteorite by single-crystal X-ray diffraction and Mössbauer spectroscopy. The Fe 2+-Mg ordering closure temperatures obtained by X-ray structure refinement for two orthopyroxe...

We report an experimental study of the intracrystalline distribution of Fe 2+ and Mg between the non-equivalent octahedral sites, M1 and M2, in orthopyroxene from the Kapoeta meteorite by single-crystal X-ray diffraction and Mössbauer spectroscopy. The Fe 2+-Mg ordering closure temperatures obtained by X-ray structure refinement for two orthopyroxe...

Folvikite, Sb ⁵⁺ Mn ³⁺ (Mg,Mn ²⁺ ) 10 O 8 (BO 3 ) 4 , is a new oxyborate mineral from the Kitteln mine, Värmland, Sweden, where it occurs as a primary skarn mineral embedded in calcite. It forms striated prismatic crystals up to 0.3 mm, and is black to dark reddish-brown with submetallic lustre and a reddish-brown streak. It is brittle, has a Mohs...

In this work we report on a complete crystal-chemical characterization of a near end-member riebeckite from Malawi, and use the available data to critically compare information obtained from different analytical methods. The sample occurs as well-formed and very large single crystals in pegmatitic rocks. Accurate site-populations were determined by...

The crystal structure of gianellaite, [(NHg 2) 2 ](SO 4)(H 2 O) x , cubic, F 43m, a = 9.521(6) Å V = 863.1(1.6) Å 3 , Z = 4, was solved by direct methods and refined to an R 1 index of 2.1% based on 167 unique observed reflections collected on a three-circle rotating-anode (MoKα X-radiation) diffractometer equipped with multilayer optics and an APE...

The crystal structure of gianellaite, [(NHg 2) 2 ](SO 4)(H 2 O) x , cubic, F 43m, a = 9.521(6) Å V = 863.1(1.6) Å 3 , Z = 4, was solved by direct methods and refined to an R 1 index of 2.1% based on 167 unique observed reflections collected on a three-circle rotating-anode (MoKα X-radiation) diffractometer equipped with multilayer optics and an APE...

Bulgakite, ideally Li2(Ca,Na)Fe²⁺7Ti2(Si4O12)2O2(OH)4(O,F)(H2O)2, and nalivkinite, ideally Li2NaFe²⁺7 Ti2(Si4O12)2O2(OH)4F(H2O)2, are astrophyllite-supergroup minerals. Bulgakite is a new mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, in the area of the joint Turkestansky, Zeravshansky, and Alaisky ridges,...

The crystal structure and chemical formula of bafertisite, Ba2Fe²⁺4Ti2(Si2O7)2O2(OH)2F2, have been revised. Three samples of bafertisite were studied using electron-microprobe analysis, Mossbauer spectroscopy, IR and Raman spectroscopy, and single-crystal X-ray diffraction. These samples are from (1) the Bayan Obo REE deposit, Inner Mongolia, China...

Bobshannonite, Na2KBa(Mn,Na)8(Nb,Ti)4(Si2O7)4O4(OH)4(O,F)2, is a new TS-block mineral from Mont Saint-Hilaire, Québec, Canada. It occurs as blocky crystals 0.5-1 mm across, perched on sérandite and albite. Other associated minerals are epididymite, catapleiite, aegirine, kupletskite, rhodochrosite and rhabdophane-(Ce). Bobshannonite occurs as vitre...

Anzaite-(Ce), ideally Ce3+ 4Fe2+Ti6 O18 (OH)2, is a new, structurally complex mineral occurring as scarce minute crystals in hydrothermally altered silicocarbonatites in the Afrikanda alkali-ultramafic complex of the Kola Peninsula, Russia. The mineral is a late hydrothermal phase associated with titanite, hibschite, clinochlore and calcite replaci...

Gerasimovskiy and Kazakova (1962) described betalomonosovite, Na2Ti2Si2O9B(Na,H)3PO4, from the Lovozero alkaline massif, Kola Peninsula, Russia. The crystal structure of the mineral was studied five times, each time resulting in a different formula. However, agreement between the crystal structure and the chemical analysis has never been reached. T...

Khvorovite, ideally Pb2+4Ca2[Si8B2(SiB)O28]F, is a new borosilicate mineral of the hyalotekite group from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, Tajikistan. Khvorovite was found in a pectolite aggregate in silexites (quartz-rich rocks). The pectolite aggregate consists mainly of pectolite, quartz and fluorite,...

The crystal structure of pargasite from a cut gem from Myanmar, (K 0.094 Na 0.93)(Na 0.15 Ca 1.78)(Mg 4.51 Fe 2+ 0.02 Al 0.53 Ti 0.10) (Si 6.56 Al 1.44)O 22 (OH 1.32 F 0.68), a 9.882(6), b 17.973(11), c 5.282(3) Å, β 105.20(1)°, V 905.33(17) Å 3 , space group C2/m, Z = 2, has been refined to an R 1 index of 1.9% using MoKα single-crystal X-ray diff...

AbStrACt Yusupovite, ideally Na 2 Zr(Si 6 O 15)(H 2 O) 3 , is a new silicate mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, area of the joint Turkestansky, Zeravshansky, and Alaisky ridges, Tajikistan. Yusupovite was found in a pegmatite composed mainly of reedmergnerite, aegirine, microcline, and polylith...

The crystal structure of betalomonosovite, ideally Na6□4Ti4 (Si2O7)2 [PO3 (OH)][PO2 (OH) 2]O2 (OF), a 5.3331(7), b 14.172 (2), c 14.509(2) Å, α 103.174(2), β 96.320(2), γ 90.278(2)°, V 1060.7(4) Å3, from the Lovozero alkaline massif, Kola peninsula, Russia, has been refined in the space group P1 to R = 6.64% using 3379 observed (Fo > 4σF) reflectio...

The southeastern part of the Nanling metallogenic province, China is host to numerous granite-hosted vein-type hydrothermal uranium deposits. The geology and geochemistry of these deposits have been extensively studied. However, accurate and precise ages for the uranium mineralization are scarce because the uranium minerals in these deposits are us...

Ferro-ferri-nybøite, NaNa2(Fe32+Fe23+)Si8O22(OH)2, is a new mineral of the amphibole group from Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie (formerly Rouville County), Québec, Canada. It occurs in an igneous microbreccia associated with a eudialyte-group mineral, an astrophyllite-group mineral, albite, and nepheline...

Ferro-ferri-nybøite, NaNa 2 (Fe 2+ 3 Fe 3+ 2)(Si 7 Al)O 22 (OH) 2 , is a new mineral of the amphibole group from Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie (formerly Rouville County), Québec, Canada. It occurs in an igneous microbreccia associated with a eudialyte-group mineral, an astrophyllite-group mineral, albi...

The crystal structure of nafertisite, Na3Fe2+10Ti2(Si6O17)2O2(OH)6F(H2O)2, from Mt. Kukisvumchorr, Khibiny alkaline massif, Kola peninsula, Russia, a 5.358(1), b 16.204(3), c 21.976(4) Å, β 94.91(1)˚, V 1901.0(7) Å3, space group A2/m, Z = 2, D calc. 3.116 g/cm3, has been refined to an R 1 value of 5.60 % for 2747 observed [F o > 4σF] unique reflect...

Agakhanovite-(Y), ideally (YCa)□2KBe3Si12O30, is a new milarite-group mineral from the Heftetjern pegmatite, Tørdal, southern Norway. Crystals are prismatic along [001], and show the forms {100} and {100}. Agakhanovite-(Y) is colorless with a white streak and a vitreous luster, and does not fluoresce under ultraviolet light. There is no cleavage or...

Introduction: Patos de Minas (hexahedrite: 5.36 wt% Ni) shows few angular nodules of troilite with daubreelite exsolution lamellae [1]. The studied polished section has a particularly round sulfide globule (~ 4.5 mm in diameter) containing a spherical silicate inclusion (400 µm in diameter). Trace element abundances (SIMS) in the Fe-rich silicate p...

The iron-bearing phases in a ureilite fragment (AS#051) from the Almahata Sitta meteorite are studied using Mössbauer spectroscopy, X-ray diffraction (XRD), and electron microprobe analysis (EMPA). AS#051 has a typical ureilite texture of medium- to coarse-grained silicates (olivine, orthopyroxene, and pigeonite) with minor opaques (Fe-Ni metal, tr...

Saamite, Ba square TiNbNa3Ti(Si2O7)(2)O-2(OH)(2)(H2O)(2), is a Group-III TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as transparent platy crystals 210 mu m thick and up to 180 mu m across. It is colorless to very pale tan, with a white streak and a vitreous luste...

Vladykinite, ideally Na3Sr4(Fe2+Fe3+)Si8O24, is a new complex sheet silicate occurring as abundant prismatic crystals in a dike of coarse-grained peralkaline feldspathoid syenite in the north-central part of the Murun complex in eastern Siberia, Russia (Lat. 58 degrees 22 ' 48 '' N; Long. 119 degrees 03 ' 44 '' E). The new mineral is an early magma...

The crystal structure of comancheite, Hg2+55N3–24(OH, NH2)4(Cl,Br)34, orthorhombic, space group Pnnm, a = 18.414(5), b = 21.328(6), c = 6.6976(19) Å, V = 2630(2) Å3, Z = 1, was solved by direct methods and refined to an R 1 index of 4.3% based on 4160 unique observed reflections. In the structure of comancheite, there are nine crystallographically...

Kolskyite (Ca square)Na2Ti4(Si2O7)(2)O-4(H2O)(7), is a Group-IV TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as single, platy crystals 2-40 mu m thick and up to 500 mu m across. It is pinkish yellow, with a white streak and a vitreous luster. The mineral formed in...

The crystal structure of comancheite, Hg 2+ 55 N 3À 24 (OH,NH 2) 4 (Cl , Br) 34 , orthorhombic, space group Pnnm, a = 18.414(5), b = 21.328(6), c = 6.6976(19) Å , V = 2630(2) Å 3 , Z = 1, was solved by direct methods and refined to an R 1 index of 4.3% based on 4160 unique observed reflections. In the structure of comancheite, there are nine crysta...

The crystal structure of schiillerite, ideally Na2Ba2Mg2Ti2(Si2O7)(2)O2F2, a 5.396(1), b 7.071(1), c 10.226(2) angstrom, alpha 99.73(3), beta 99.55(3), gamma 90.09(3)degrees, V 379.1(2) angstrom(3), Z = 1, from the Eifel volcanic region, Germany, has been refined in the space group P (1) over bar to R = 1.33% using 2247 observed (F-0> 4 sigma F) re...

Carlfrancisite, Mn32+(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, is a new mineral from the Kombat mine, Otavi Valley, Namibia, and occurs as curved platy aggregates ~2 cm across on a matrix of Mn arsenates and oxides. It is yellowy orange to pale yellow with a very pale-yellow streak, translucent with a vitreous to opal...

Three synthetic Ca-rich clinopyroxenes on the hedenbergite-ferrosilite join, with compositions (Hd 50 Fs 50), (Hd 60 Fs 40), and (Hd 70 Fs 30), were investigated by single-crystal X-ray diffraction and Mössbauer spectroscopy at room temperature. For all samples, there is no evidence for the presence of phases with symmetry other than C2/c. Structur...

Here we study cation distribution in orthopyroxenes from São João Nepomuceno meteorite by Mössbauer spectroscopy, electron microprobe and single-crystal X-ray diffraction, in order to get insights into the thermal history of this meteorite.

Here, we report the finding of nanodiamonds in carbonaceous-chondrite inclusions from the Kapoeta meteorite by Fourier-transform infrared (FTIR) and Raman spectroscopy. Our results have important implications for interstellar nanodiamonds.

Sandstone-hosted unconformity-related U deposits in the Athabasca Basin at McArthur River Zone 4 and Maurice Bay as well as barren alteration systems at Wheeler River Zone "K" and Spring Point are surrounded by an outer, peripheral zone of illite and an inner, central zone of chlorite alteration. The oxidation state of Fe determined by 57Fe Mossbau...

Three synthetic Ca-rich clinopyroxenes on the hedenbergite-ferrosilite join, with compositions (Hd(50)Fs(50)), (Hd(60)Fs(40)), and (Hd(20)Fs(30)), were investigated by single-crystal X-ray diffraction and Mossbauer spectroscopy at room temperature. For all samples, there is no evidence for the presence of phases with symmetry other than C2/c. Struc...

The crystal structure of legrandite -- Zn-2(AsO4)(OH)(H2O), monoclinic, a 12.8052(3), b 7.9249(2), c 10.2173(2) angstrom, beta 104.4329(3)degrees, V 1004.13(6) angstrom(3), space group P2(1)/c, Z = 2 -- has been refined to an R-1 value of 1.2% based on 2844 unique [vertical bar F-o vertical bar > 4 sigma F] reflections measured with a Bruker D8 thr...

The crystal structure of yofortierite, (Mn2+, Mg, Fe3+, square) 5Si8O20(OH, H2O)(2)(H2O)(7), monoclinic, C2/m, Z = 4, a 14.1686(12), b 17.8583(16), c 5.2919(5) angstrom, beta 105.878(1)degrees, V 1287.9(3) angstrom(3), has been refined to R-1 = 4.9 % for 1795 unique (F-o > 4 sigma F) reflections collected on a Bruker D8 three-circle diffractometer...

Wopmayite ideally Ca6Na3 square Mn(PO4)(3)(PO3OH)(4), is a new secondary mineral from the Tanco mine, Bernic Lake, Manitoba. It occurs in vugs in a single 5-10 cm mass of phosphate-carbonate mineralization in a spodumene-rich boulder found in the dumps of the Tanco Mine, Bernic Lake, Manitoba, Canada. It is a secondary mineral that crystallized tog...

Schlüterite-(Y), ideally (Y,REE)2Al(Si2O7)(OH)2F, is a new silicate mineral species from the Stetind pegmatite, Tysfjord, Nordland, Norway. It forms dense, fibrous, radiating aggregates (up to ∼2 mm) diverging to individual needle-like crystals (up to ∼1 mm long) in cavities. Crystals are acicular to bladed, flattened on {001} and elongated along [...

Fluor-elbaite,Na(Li1.5Al1.5)Al-6(Si6O18)(BO3)(3)(OH)(3)F, is a new mineral of the tourmaline supergroup. It is found in miarolitic cavities in association with quartz, pink muscovite, lepidolite, spodumene, spessartine, and pink beryl in the Cruzeiro and Urubu mines (Minas Gerais, Brazil), and apparently formed from late-stage hydrothermal solution...

Billwiseite ideally Sb-5(3+)(Nb,Ta)(3)WO18, is an oxide mineral from a granitic pegmatite on the eastern margin of the Nanga Parbat - Haramosh massif at Stak Nala, 70 km east of Gilgit, Pakistan. It is transparent, pale yellow (with a tinge of green), has a colorless to very pale-yellow streak, a vitreous luster, and is inert to ultraviolet radiati...

Aspedamite ideally square(12)(Fe3+,Fe2+)(3)Nb-4[Th(Nb,Fe3+)(12)O-42]{(H2O),(OH)}(12), is a new heteropolyniobate mineral species from the Herrebokasa quarry, Aspedammen, Ostfold, southern Norway. It occurs as small euhedral crystals of dodecahedra and cubes to a maximum of 50 mu m across, perched on a white mat of an Al-Nb-Fe-Ti-Ca-K-bearing silica...

Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite...

Spherical particles have been sampled from soils and silica-rich rock coatings close to major smelter centers at Coppercliff, Coniston, and Falconbridge in the Sudbury area, Canada. Detailed analyses employing optical microscopy, scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy, and Mössbauer spectroscopy hav...

The effects of planar defects and composition on Ar mobility in trioctahedral micas have been investigated in samples from a small marble outcrop (∼500 m2) in the Frontenac Terrane, Grenville Province, Ontario. These micas crystallized during amphibolite-facies metamorphism at ∼1170 Ma and experienced a thermal pulse ∼100 Ma later at shallow crusta...

Tourmalines of unusual (mushroom) habit are common in granitic pegmatites of Momeik, northeast of Mogok, Myanmar. Here, we examine a sample of elbaite of significantly different habit, consisting of a series of diverging crystals, resembling a sheaf of wheat and ranging in colour from light purplish-red at the base to dark purplish-red at the tip w...

Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (∼10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 μm in size. The crystals occur as aggregates (up to 500 μm across) of subparallel to slightly diverging prisms...

The crystal structures of green (brown) variants of manitobaite, ideally (Na-16 square)Mn252+Al8(PO4)(30), monoclinic, Pc, Z = 2: green: a 13.4517(7), b 12.5266(7), c 26.6765(13) angstrom, beta 101.582(1)degrees, V 4403.6(7) angstrom(3), D-calc. 3.642 g/cm(3); brown: 13.4499(6), b 12.5046(5), c 26.6148(11) angstrom, beta 101.221(1)degrees, V 4390.7...

Sveinbergeite, Ca(Fe2+6Fe3+)Ti2(Si4O12)2O2(OH)5(H2O)4, is a new astrophyllite-group mineral discovered in a syenite pegmatite at Buer on the Vesterøya peninsula, Sandefjord, Oslo Region, Norway. The mineral occurs in pegmatite cavities as 0.01–0.05 mm thick lamellar (0.2–0.5 × 5–10 mm) crystals forming rosette-like divergent groups and spherical ag...

Eight turquoise samples covering a wide range of compositions in the turquoise-chalcosiderite solid-solution series were analyzed by Mössbauer spectroscopy, X-ray diffraction (XRD), electron microprobe analysis (EMPA), and Fourier transform infrared (FTIR) spectroscopy. Two of the turquoise samples display evidence of alteration from weathering pro...

Eight turquoise samples covering a wide range of compositions in the turquoise-chalcosiderite solid-solution series were analyzed by Mössbauer spectroscopy, X-ray diffraction (XRD), electron microprobe analysis (EMPA), and Fourier transform infrared (FTIR) spectroscopy. Two of the turquoise samples display evidence of alteration from weathering pro...

Tourmalines of unusual (mushroom) habit are common in granitic pegmatites of Momeik, northeast of Mogok, Myanmar. Here, we examine a sample of elbaite of significantly different habit, consisting of a series of diverging crystals, resembling a sheaf of wheat and ranging in colour from light purplish-red at the base to dark purplish-red at the tip w...

The crystal structures of 23 samples extracted from a large slice oriented along (001) of a single crystal of liddicoatite from the Anjanabonoina granitic pegmatite in Madagascar (showing pronounced, visually discontinuous oscillatory zones and anomalous biaxiality) were refined to R1 indices of 1.5-2.9% (< R-1 > = 1.78%). Cell parameters are in th...

The crystal structures of 23 samples extracted from a large slice oriented along (001) of a single crystal of liddicoatite from the Anjanabonoina granitic pegmatite in Madagascar (showing pronounced, visually discontinuous oscillatory zones and anomalous biaxiality) were refined to R1 indices of 1.5-2.9% (<R 1 > = 1.78%). Cell parameters are in the...