scholarly journals On the Color and Genesis of Prase (Green Quartz) and Amethyst from the Island of Serifos, Cyclades, Greece

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 487 ◽  
Author(s):  
Stephan Klemme ◽  
Jasper Berndt ◽  
Constantinos Mavrogonatos ◽  
Stamatis Flemetakis ◽  
Ioannis Baziotis ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Oxygen Isotope ◽  
Electron Microprobe ◽  
Crystallization Process ◽  
Mineral Chemistry ◽  
Quartz Crystals ◽  
Two Generations ◽  
Dispersed Inclusions ◽  
Isotope Measurements

The color of quartz and other minerals can be either caused by defects in the crystal structure or by finely dispersed inclusions of other minerals within the crystals. In order to investigate the mineral chemistry and genesis of the famous prase (green quartz) and amethyst association from Serifos Island, Greece, we used electron microprobe analyses and oxygen isotope measurements of quartz. We show that the color of these green quartz crystals is caused by small and acicular amphibole inclusions. Our data also shows that there are two generations of amphibole inclusions within the green quartz crystals, which indicate that the fluid, from which both amphiboles and quartz have crystallized, must have had a change in its chemical composition during the crystallization process. The electron microprobe data also suggests that traces of iron may be responsible for the amethyst coloration. Both quartz varieties are characterized by isotopic compositions that suggest mixing of magmatic and meteoric/marine fluids. The contribution of meteoric fluid is more significant in the final stages and reflects amethyst precipitation under more oxidizing conditions.

New arsenate minerals from the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. XI. Anatolyite, Na6(Ca,Na)(Mg,Fe3+)3Al(AsO4)6

2019 ◽  
Vol 83 (5) ◽  
pp. 633-638 ◽  
Author(s):  
Igor V. Pekov ◽  
Inna S. Lykova ◽  
Vasiliy O. Yapaskurt ◽  
Dmitry I. Belakovskiy ◽  
Anna G. Turchkova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Electron Microprobe ◽  
New Mineral ◽  
Single Crystal Xrd ◽  
Xrd Pattern ◽  
Potassic Feldspar ◽  
Tolbachik Volcano ◽  
Mohs Hardness ◽  
Heteropolyhedral Framework

AbstractThe new mineral anatolyite Na6(Ca,Na)(Mg,Fe3+)3Al(AsO4)6 was found in the Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. It is associated with potassic feldspar, hematite, tenorite, cassiterite, johillerite, tilasite, ericlaxmanite, lammerite, arsmirandite, sylvite, halite, aphthitalite, langbeinite, anhydrite, wulffite, krasheninnikovite, fluoborite, pseudobrookite and fluorophlogopite. Anatolyite occurs as aggregates (up to 2 mm across) of rhombohedral–prismatic, equant or slightly elongated along [001] crystals up to 0.2 mm. The mineral is transparent, pale brownish–pinkish, with vitreous lustre. It is brittle, cleavage was not observed and the fracture is uneven. The Mohs’ hardness is ca 4½. Dcalc is 3.872 g cm–3. Anatolyite is optically uniaxial (–), ω = 1.703(4) and ε = 1.675(3). Chemical composition (wt.%, electron microprobe) is: Na2O 16.55, K2O 0.43, CaO 2.49, MgO 5.80, MnO 0.16, CuO 0.69, ZnO 0.55, Al2O3 5.01, Fe2O3 7.94, TiO2 0.18, SnO2 0.17, SiO2 0.04, P2O5 0.55, As2O5 60.75, SO3 0.03, total 101.34. The empirical formula based on 24 O apfu is (Na5.90K0.10)Σ6.00(Ca0.50Na0.13Zn0.08Mn0.03)Σ0.74(Mg1.63Fe3+1.12Al0.15Cu0.10)Σ3.00(Al0.96Ti0.03Sn0.01)Σ1.00(As5.97P0.09Si0.01)Σ6.07O24. Anatolyite is trigonal, R$\bar{3}$c, a = 13.6574(10), c = 18.2349(17) Å, V = 2945.6(4) Å3 and Z = 6. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 7.21(33)(012), 4.539(16)(113), 4.347(27)(211), 3.421(20)(220), 3.196(31)(214), 2.981(17)(223), 2.827(100)(125) and 2.589(18)(410). The crystal structure was solved from single-crystal XRD data to R = 4.77%. The structure is based on a 3D heteropolyhedral framework formed by M4O18 clusters [M1 = Al and M2 = (Mg,Fe3+)] linked with AsO4 tetrahedra. (Ca,Na) and Na cations centre A1O6 and A2O8 polyhedra in voids of the framework. Anatolyite is isostructural with yurmarinite. The new mineral is named in honour of the outstanding Russian crystallographer, mineralogist and mathematician Anatoly Kapitonovich Boldyrev (1883–1946).

The crystal structure of kraisslite,[4]Zn3(Mn, Mg)25(Fe3+,Al)(As3+O3)2[(Si,As5+)O4]10(OH)16, from the Sterling Hill mine, Ogdensburg, Sussex County, New Jersey, USA

2012 ◽  
Vol 76 (7) ◽  
pp. 2819-2836 ◽  
Author(s):  
M. A. Cooper ◽  
F. C. Hawthorne
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Hydrogen Bonds ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Lone Pair ◽  
Direct Methods ◽  
Sussex County ◽  
Lower Site

AbstractThe crystal structure of kraisslite, orthorhombic (pseudo-hexagonal),a= 8.1821(1),b= 14.1946(3),c= 43.9103(8) Å,V= 5099.8(2) Å3,Z= 4 anddcalc= 4.083 g cm–3, has been solved by direct methods and refined in the space groupC2221to anR1index of 1.68% for 7432 observed (|Fo| > 4σ|F|) reflections. Electron-microprobe analysis gave the following chemical composition: As2O510.86, As2O36.18, SiO213.39, Al2O30.25, Fe2O32.06, MnO 51.14, ZnO 7.39, MgO 2.13, CaO 0.05, H2Ocalc= 4.50, sum 97.95 wt.%; and empirical formula: Zn2.91(Mn23.07Mg1.69Ca0.03)Σ=24.79(Fe0.833+Al0.16)Σ=0.99(As3+O3)2[(Si0.71As0.305+)O4]10(OH)16calculated on the basis of 62 anions with (OH) = 16 and As3+/(As3++ As5+) taken from the refined crystal structure. The general formula, [4]Zn3(Mn,Mg)25(Fe3+,Al)(As3+O3)2[(Si,As5+)O4]10(OH)16, differs from those given previously.There is one As3+site with a <As–O> distance of 1.780 Å and a stereochemistry typical of a stereoactive lone-pair of electrons. There are five tetrahedrally coordinated T sites with <T–O> distances from 1.635 to 1.692 Å; the T(1) site is fully occupied by As5+, and the T(2)–T(5) sites are occupied by both Si and As5+. There are two tetrahedrally coordinated Zn sites with <T–O> distances of ∼1.996 Å, both of which are occupied by dominant Zn and minor Mn2+. There are thirteen octahedrally coordinated M sites, twelve of which are occupied by dominant Mn2+with lesser Mg and minor Zn; <M–O> distances are in the range 2.197–2.284 Å. The <M(13)–O> distance is 2.083 Å and its lower site scattering indicates occupancy by Fe3+, Mn2+, Mg and Al. The structure consists of five crystallographically distinct layers of polyhedra, labelled m = 0 – 4. Layer m = 0 consists of corner-sharing Zn and (Si, As5+) tetrahedra, and layers m = 1–4 each consist of trimers of Mn2+octahedra linked by (Si, As5+) tetrahedra and intrasheet hydrogen bonds (m = 1, 3) or (Si, As5+) tetrahedra and (Fe3+,Al) octahedra (m = 2) or (As5+) tetrahedra and (As3+O3) triangular pyramids and intrasheet hydrogen bonds (m = 4). The layers stack along [001] with reversals of the sequence m = 1, 2, 3, 4 at z = 0, ¼, ½ and ¾. Kraisslite is a member of the mcgovernite family.

scholarly journals A New Mineral Ferrisanidine, K[Fe3+Si3O8], the First Natural Feldspar with Species-Defining Iron

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 770 ◽  
Author(s):  
Nadezhda Shchipalkina ◽  
Igor Pekov ◽  
Sergey Britvin ◽  
Natalia Koshlyakova ◽  
Marina Vigasina ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Electron Microprobe ◽  
Empirical Formula ◽  
Rietveld Method ◽  
Kamchatka Peninsula ◽  
Scoria Cone ◽  
Unit Cell ◽  
New Mineral ◽  
Tolbachik Volcano

Ferrisanidine, K[Fe3+Si3O8], the first natural feldspar with species-defining iron, is an analogue of sanidine bearing Fe3+ instead of Al. It was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Fissure Tolbachik Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. The associated minerals are aegirine, cassiterite, hematite, sylvite, halite, johillerite, arsmirandite, axelite, aphthitalite. Ferrisanidine forms porous crusts composed by cavernous short prismatic crystals or irregular grains up to 10 μm × 20 μm. Ferrisanidine is transparent, colorless to white, the lustre is vitreous. Dcalc is 2.722 g·cm−3. The chemical composition of ferrisanidine (wt. %, electron microprobe) is: Na2O 0.25, K2O 15.15, Al2O3 0.27, Fe2O3 24.92, SiO2 60.50, in total 101.09. The empirical formula calculated based on 8 O apfu is (K0.97Na0.03)Ʃ1.00(Si3.03Fe3+0.94Al0.02)Ʃ3.99O8. The crystal structure of ferrisanidine was studied using the Rietveld method, the final R indices are: Rp = 0.0053, Rwp = 0.0075, R1 = 0.0536. Parameters of the monoclinic unit cell are: a = 8.678(4), b = 13.144(8), c = 7.337(5) Å, β = 116.39(8)°, V = 749.6(9) Å3. Space group is C2/m. The crystal structure of ferrisanidine is based on the sanidine-type “ferrisilicate” framework formed by disordered [SiO4] and [Fe3+O4] tetrahedra.

scholarly journals Mn-nabohacené tetraedrity z rumunských ložisek Cavnic, Botești a Săcărâmb

2020 ◽  
Vol 28 (1) ◽  
pp. 161-169
Author(s):  
Dalibor Velebil ◽  
Jiří Sejkora ◽  
Zdeněk Dolníček
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Electron Microprobe

Eight samples of members of tetrahedrite group from Romanian deposits were examined in terms of their chemical composition studied by means of electron microprobe; five samples from Cavnic, two from Botești and one from Săcărâmb. Mean composition of all samples is corresponding to tetrahedrite-(Zn) and most of them contain Mn. The three Cavnic tetrahedrites contain up to 0.17 apfu, the two Botești samples contain up to 0.42 apfu and the Săcărâmb sample up to 0.83 apfu Mn. Pb and Sn were present at levels up to 0.01 apfu but entering of Pb and Sn into the crystal structure of tetrahedrite group minerals is questionable. In spite of the significant presence of Te is characteristic for the Botești and Săcărâmb deposits, the studied tetrahedrites from these deposits are virtually Te-free (only locally contents of Te up to 0.05 apfu were detected in one sample).

scholarly journals From structure topology to chemical composition. VI. Titanium silicates: the crystal structure and crystal chemistry of bornemanite, a group III Ti-disilicate mineral

2007 ◽  
Vol 71 (06) ◽  
pp. 593-610 ◽  
Author(s):  
F. Cámara ◽  
E. Sokolova
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Titanium Silicate ◽  
Group Iii ◽  
Structure Topology ◽  
Titanium Silicates ◽  
Alkaline Massif

Abstract The crystal structure of bornemanite, ideally Na6☐BaTi2Nb(Si2O7)2(PO4)O2(OH)F, a = 5.4587(3), b = 7.1421(5), c = 24.528(2) Å, α = 96.790(1), β = 96.927(1), γ = 90.326(1)°, V = 942.4(2) Å3, space group (P1̄), Z = 2, Dcalc. = 3.342 g cm–3, from the Lovozero alkaline massif, Kola Peninsula, Russia, has been solved and refined to R1 = 6.36% on the basis of 4414 unique reflections (Fo &gt;4sF). Electron microprobe analysis yielded the empirical formula (Na6.07Mn2+ 0.23Ca0.06☐0.64)Σ 7.00 (Ba0.73K0.13Sr0.06☐0.08)Σ 1.00(Ti2.05Nb0.80Zr0.02Ta5+ 0.01Fe3+ 0.03Al0.02Mn2+ 0.06Mg0.01)Σ 3.00(Si2O7)2(P0.97O4)O2 [F1.27(OH)0.74]Σ 2.01. The crystal structure of bornemanite is a combination of a TS (titanium silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for Group III (Ti = 3 a.p.f.u.) of Ti-disilicate minerals: two H sheets connect to the O sheet such that two (Si2O7) groups link to the trans edges of a Ti octahedron of the O sheet. The O sheet cations give Na3Ti (4 a.p.f.u.). The TS block has two different H sheets, H1 and H2, where (Si2O7) groups link to [5]Ti and [6]Nb polyhedra, and there are two peripheral sites which are occupied by Ba and Na, respectively. There are two I blocks: the I1 block is a layer of Ba atoms; the I2 block consists of Na polyhedra and (PO4) tetrahedra.

Structural/Property Relationships for Optical Materials

1993 ◽  
Vol 329 ◽  
Author(s):  
Vivien D.
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Electronic Structure ◽  
Chemical Composition ◽  
Field Strength ◽  
Optical Materials ◽  
Site Occupancy ◽  
Laser Materials ◽  
Crystal Field Strength ◽  
The Matrix

AbstractIn this paper the relationships between the crystal structure, chemical composition and electronic structure of laser materials, and their optical properties are discussed. A brief description is given of the different laser activators and of the influence of the matrix on laser characteristics in terms of crystal field strength, symmetry, covalency and phonon frequencies. The last part of the paper lays emphasis on the means to optimize the matrix-activator properties such as control of the oxidation state and site occupancy of the activator and influence of its concentration.

Using stable hydrogen and oxygen isotope measurements of feathers to infer geographical origins of migrating European birds

Oecologia ◽  
2004 ◽  
Vol 141 (3) ◽  
pp. 477-488 ◽  
Author(s):  
Keith A. Hobson ◽  
Gabriel J. Bowen ◽  
Leonard I. Wassenaar ◽  
Yves Ferrand ◽  
Hervé Lormee
Keyword(s):  
Oxygen Isotope ◽  
Hydrogen And Oxygen Isotope ◽  
Isotope Measurements

From Structure Topology to Chemical Composition. XXIX. Revision of the Crystal Structure of Perraultite, NaBaMn4Ti2(Si2O7)2O2(OH)2F, a Seidozerite-Supergroup TS-Block Mineral from the Oktyabr'skii Massif, Ukraine, and Discreditation of Surkhobite

2021 ◽  
Author(s):  
Elena Sokolova ◽  
Maxwell C. Day ◽  
Frank C. Hawthorne ◽  
Atali A. Agakhanov ◽  
Fernando Cámara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Structure Type ◽  
Titanium Silicate ◽  
Space Group ◽  
Structure Topology ◽  
Ideal Composition ◽  
Using Data ◽  
Cation Sites ◽  
The Ideal

ABSTRACT The crystal structure of perraultite from the Oktyabr'skii massif, Donetsk region, Ukraine (bafertisite group, seidozerite supergroup), ideally NaBaMn4Ti2(Si2O7)2O2(OH)2F, Z = 4, was refined in space group C to R1 = 2.08% on the basis of 4839 unique reflections [Fo &gt; 4σFo]; a = 10.741(6), b = 13.841(8), c = 11.079(6) Å, α = 108.174(6), β = 99.186(6), γ = 89.99(1)°, V = 1542.7(2.7) Å3. Refinement was done using data from a crystal with three twin domains which was part of a grain used for electron probe microanalysis. In the perraultite structure [structure type B1(BG), B – basic, BG – bafertisite group], there is one type of TS (Titanium-Silicate) block and one type of I (Intermediate) block; they alternate along c. The TS block consists of HOH sheets (H – heteropolyhedral, O – octahedral). In the O sheet, the ideal composition of the five [6]MO sites is Mn4 apfu. There is no order of Mn and Fe2+ in the O sheet. The MH octahedra and Si2O7 groups constitute the H sheet. The ideal composition of the two [6]MH sites is Ti2 apfu. The TS blocks link via common vertices of MH octahedra. The I block contains AP(1,2) and BP(1,2) cation sites. The AP(1) site is occupied by Ba and the AP(2) site by K &gt; Ba; the ideal composition of the AP(1,2) sites is Ba apfu. The BP(1) and BP(2) sites are each occupied by Na &gt; Ca; the ideal composition of the BP(1,2) sites is Na apfu. We compare perraultite and surkhobite based on the work of Sokolova et al. (2020) on the holotype sample of surkhobite: space group C , R1 = 2.85 %, a = 10.728(6), b = 13.845(8), c = 11.072(6) Å, α = 108.185(6), β = 99.219(5), γ = 90.001(8)°, V = 1540.0(2.5) Å3; new EPMA data. We show that (1) perraultite and surkhobite have identical chemical composition and ideal formula NaBaMn4Ti2(Si2O7)2O2(OH)2F; (2) perraultite and surkhobite are isostructural, with no order of Na and Ca at the BP(1,2) sites. Perraultite was described in 1991 and has precedence over surkhobite, which was redefined as “a Ca-ordered analogue of perraultite” in 2008. Surkhobite is not a valid mineral species and its discreditation was approved by CNMNC IMA (IMA 20-A).

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