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Christian Bertoldi - One of the best experts on this subject based on the ideXlab platform.

  • heat pulse calorimetry measurements on natural Chlorite Group minerals
    American Mineralogist, 2007
    Co-Authors: Christian Bertoldi, Edgar Dachs, Peter Appel
    Abstract:

    Low- and high-temperature heat capacities of five natural Chlorite-Group samples were measured using the heat-capacity option of the Physical Properties Measurement System (Quantum Design), which is based on the principles of heat-pulse calorimetry, and by differential scanning calorimetry. Comprehensive chemical analyses were performed on these samples by electron microprobe analysis, by inductively coupled plasma mass spectrometry, and by Karl-Fischer titration (for H2O). The natural Chlorites span a range in X-Fe from 0.052 to 0.885 with increasing Al-content due to the Tschermak substitution with increasing X-Fe. The measured heat capacities were extrapolated to the end-member compositions of chamosite and clinochlore. Integration of heat-capacity data yields the calorimetric standard entropies of chamosite (Fe5Al)[Si3AlO10](OH)(8) and clinochlore (Mg5Al)[Si3AlO10](OH)(8), with values of 572.0 +/- 0.2 and 425.6 +/- 0.4 J/(mol-K), respectively. The C-p-polynomial for end-member chamosite is C-p = 1151.7 - 8.4564 x 10(3)-T-0.5 - 13.206 x 10(6)-T-2 + 15.233 x 10(8).T-3 [J/(mol-K)], valid in the temperature range of 298.15-900 K, and that for end-member clinochlore is C-p = 1160.5 - 9.9819 x 10(3)-T-0.5 - 5.9534 x 10(6).T-2 + 3.8677 x 10(8)-T-3 [J/(mol-K)], valid in the temperature range of 298.15-1000 K. The Fe-rich Chlorites exhibit an asymmetric distribution of the excess heat capacity in a plot of C-p(ex) vs. T, with a maximum at about 52 K. By analogy to annite, we interpret this peak to represent the magnetic ordering temperature. Based on our standard entropy value for chamosite, the enthalpy of formation of berthierine (Fe2.5Al0.5)[Si1.5Al0.5O5Y](OH)(4) was estimated as -3570.30 kJ/mol using a reported onset temperature of 70 degrees C at 16 MPa for the berthierine-chamosite polymorphic transition.

  • The Heat Capacity of the Serpentine SubGroup Mineral Berthierine (Fe_2.5Al_0.5)[Si_1.5Al_0.5O_5](OH)_4
    Clays and Clay Minerals, 2005
    Co-Authors: Christian Bertoldi, Edgar Dachs, Lado Cemic, Thomas Theye, Richard Wirth, Werner Groger
    Abstract:

    The serpentine subGroup mineral berthierine was synthesized as a metastable precursor of the Chlorite Group mineral chamosite in cold seal pressure vessels at 575°C, 0.5 GPa and f _O_2-conditions of the NNO buffer from a glass of almandine bulk composition. The run products were investigated with X-ray powder diffraction (XRD), Mossbauer spectroscopy and electron microprobe analysis. One run product was also investigated by high-resolution transmission electron microscopy (HRTEM) and its heat capacity measured by heat pulse calorimetry and by differential scanning calorimetry in the temperature range 5–323 K. The XRD and HRTEM investigations clearly showed that the periodicity along the c axis of this sample is 7 Å demonstrating that the serpentine subGroup mineral berthierine of composition (Fe^2+_1.83Fe^3+_0.33Al_0 67)[Si_1.33Al_0.67O_5](OH)_4 has formed in the synthesis experiments. Integration of our heat capacity data, corrected to the composition (Fe_2.5Al_0.5)[Si_1.5Al_0.5O_5](OH)_4 for end-member berthierine, yields a standard entropy of 284.1±0.3 J mol^−1 K^−1. The C _p polynomial C _p = 610.72 − 5140.0 × T ^−0.5 − 5.8848 × 10^6 T ^−2 + 9.5444 × 10^8 T ^–3 is recommended for thermodynamic calculations above 298 K involving berthierine.

  • The heat capacity of the serpentine subGroup mineral berthierine (Fe2.5Al0.5) Si1.5Al0.5O5 (OH)(4)
    Clays and Clay Minerals, 2005
    Co-Authors: Christian Bertoldi, Edgar Dachs, L Cemic, Thomas Theye, Richard Wirth, Werner Groger
    Abstract:

    The serpentine subGroup mineral berthierine was synthesized as a metastable precursor of the Chlorite Group mineral chamosite in cold seal pressure vessels at 575 degrees C, 0.5 GPa and f(O2) -conditions of the NNO buffer from a glass of almandine bulk composition. The run products were investigated with X-ray powder diffraction (XRD), Mossbauer spectroscopy and electron microprobe analysis. One run product was also investigated by high-resolution transmission electron microscopy (HRTEM) and its heat capacity measured by heat pulse calorimetry and by differential scanning calorimetry in the temperature range 5-323 K. TheXRD and HRTEM investigations clearly showed that the periodicity along the e axis of this sample is 7 A demonstrating that the serpentine subGroup mineral berthierine of composition (Fe1832+Fe0.333+Al0.67)-Fe-.)[Si1.33Al0.67O5](OH)(4) has formed in the synthesis experiments. Integration of our heat capacity data, corrected to the composition (Fe2.5Al0.5)[Si1.5Al0.5O5](OH)(4) for end-member berthicrine, yields a standard entropy of 284.1 +/- 0.3 J mol(-1) K-1. The C-p polynomial C-p = 610.72 - 5140.0 x T-0.5 - 5.8848 x 10(6) T-2 + 9,5444 x 10(8) T-3 is recommended for thermodynamic calculations above 298 K involving berthierine.

  • the heat capacity of two natural Chlorite Group minerals derived from differential scanning calorimetry
    Pacific Rim Conference on Multimedia, 2001
    Co-Authors: Christian Bertoldi, Artur Benisek, L Cemic, Edgar Dachs
    Abstract:

    The heat capacity of natural chamosite (X-Fe = 0.889) and clinochlore (X-Fe = 0.116) were measured by differential scanning calorimetry (DSC). The samples were characterised by X-ray diffraction, microprobe analysis and Mossbauer spectroscopy. DSC measurements between 143 and 623 K were made following the procedure of Bosenick et al. (1996). The fitted data for natural chamosite (CA) in J mol-l K-L give: C-p.CA = 1224.3-10.685 x 10(3) x T-0.5 - 6.4389 x 10(6) x T-2 + 8.0279 x 10(8) x T-3 and for the natural clinochlore (CE): C-p.CE 1200.5-10.908 X 10(3) x T-0.5 -5.6941 x 10(6) x T-2 + 7.1166 x 10(8) x T-3. The corrected C-p-polynomial for pure end-member chamosite (Fe5Al)[Si3AlO10](OH)(8) is C-p.CAcor = 1248.3-11.116 X 10(3) x T-0.5 - 5.1623 x 10(6) x T-2 + 7.1867 x 10(8) x T-3 and the corrected C-p-polynomial for pure end-member clinochlore (Mg5Al)[Si3AlO10](OH)(8) is C-p.CEcor = 1191.3-10.665 x 10(3) x T-0.5 -6.5136 X 10(6) X T-2 + 7.7206 x 10(8) x T-3. The corrected C-p-polynomial for clinochlore is in excellent agreement with that in the internally consistent data sets of Berman (1988) and Holland and Powell (1998). The derived C-p-polynomial for chamosite (Cp.CAcor) leads to a 4.4% higher heat capacity, at 300 K, compared to that estimated by Holland and Powell (1998) based on a summation method. The corrected C-p-polynomial (C-p.CAcor) is, however, in excellent agreement with the computed C-p-polynomial given by Saccocia and Seyfried (1993), thus supporting the reliability of Berman and Brown's (1985) estimation method of heat capacities.

V. N. Rudashevsky - One of the best experts on this subject based on the ideXlab platform.

  • Skaergaardite, PdCu, a new platinum-Group intermetallic mineral from the Skaergaard intrusion, Greenland
    Mineralogical Magazine, 2020
    Co-Authors: N. S. Rudashevsky, Andrew M. Mcdonald, Louis J. Cabri, Chris J. Stanley, Troels F.d. Nielsen, Yu. L. Kretzer, V. N. Rudashevsky
    Abstract:

    Skaergaardite, PdCu, is a new mineral discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. It occurs in a tholeitiic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules composed of bornite, chalcocite, digenite, chalcopyrite, with rare cobalt pentlandite, cobaltoan pentlandite, sphalerite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au) and Pt-Fe-Cu-Pd alloys, unnamed PdCu3, (Pd,Cu,Sn), Au3Cu and PdAuCu. Skaergaardite occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and as irregular grains that vary in size from 2 to 75 mm, averaging 22 mm. It is steel grey with a bronze tint, has a black streak, a metallic lustre and is sectile. Neither cleavage nor fracture was observed. The mineral has a micro-indentation hardness of VHN25 = 257. It is isotropic, non-pleochroic and exhibits neither discernible internal reflections nor evidence of twinning. Skaergaardite varies from bright creamy white (associated with bornite and chalcopyrite) to bright white (associated with digenite and chalcocite). Reflectance values in air (and in oil) are: 58.65 (47.4) at 470 nm, 62.6 (51.1) at 546 nm, 64.1 (52.8) at 589 nm and 65.25 (53.95) at 650 nm. The average of 311 electron-microprobe analyses gives: Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28 and Pb 0.39, total 9 9.19 w t.%, c orresponding t o ( Pd 0.967 Au 0.020 Pt 0.010 )S 0.997 (Cu 0.820 Fe 0.120 Zn0.039Sn0.016Te0.004Pb0.003)S1.002. The mineral is cubic, space Group Pm3m, a = 3.0014(2) A ˚ , V = 27.0378 A ˚ 3 , Z =1 .Dcalc is 10.64 g/cm 3 . The six strongest lines in the X-ray powder-diffraction pattern [d inA ˚ (I)(hkl)] are: 2.122(100)(110), 1.5000(20)(200), 1.2254(50)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321). The mineral has the CsCl-type structure. It is believed to be isostructural with wairauite (CoFe), synthetic CuZn (b-brass) and is structurally related to hongshiite (PtCu). Skaergaardite developed from a disordered Pd-Cu-rich metal alloy melt that had exsolved from an earlier Cu-(Fe) sulphide melt. Ordering of Pd and Cu (beginning at T & 600oC) results in development of the CsCl structure from a disordered face-centred cubic structure.

  • Garutiite, (Ni,Fe,Ir), a new hexagonal polymorph of native Ni from Loma Peguera, Dominican Republic
    European Journal of Mineralogy, 2010
    Co-Authors: Andrew M. Mcdonald, Joaquín A. Proenza, Federica Zaccarini, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Joan Carles Melgarejo, John F. Lewis, Francisco Longo
    Abstract:

    Garutiite (Ni,Fe,Ir) is a new hexagonal polymorph of native Ni discovered in chromitite from Loma Peguera, Dominican Republic. The mineral was identified in heavy mineral concentrates obtained through the use of electric pulse disaggregation (EPD) and hydroseparation (HS) techniques. It forms as anhedral, botryoidal grains typically 10–60 μm in size (maximum of 110 μm). Grains are single or composite, frequently porous and zoned, and occasionally display an unusual lamellar internal texture. Associated minerals include hexaferrum, ferrian chromite, Chlorite-Group minerals, serpentine-Group minerals, awaruite, irarsite, laurite, native Ru and unidentified species including Ru–Os–Ir-Fe and Pt–Ni–Fe–Ir compounds, Pt(Ni,Fe)3, (Fe,Ru,Ni,Os,Ir,Co)2S and RhNiAs. The mineral is megascopically grey to grey-black with a metallic luster. In plane-polarized light, garutiite is white in color, exhibits a very weak anisotropy, and no pleochroism, bireflectance or internal reflections were observed. No cleavage was noted and the hardness could not be determined owing to the porous nature of the mineral. The calculated density is 11.33 (1) g/cm3. Reflectance values (%) in air are: 63.8 at 470, 65.9 at 546, 67.0 at 589 and 68.0 at 650 nm. The average result of electron microprobe analyses ( n = 42 from 27 grains) is: Ni 27.91, Fe 19.94, Ir 43.78, Pt 6.98, Co 0.55, Cu 0.43, Ru, 0.50, Rh 0.74, Os 0.67, total 101.51 wt%, corresponding to (Ni0.421Fe0.316Ir0.202Pt0.032Co0.008Cu0.006Rh0.006Ru0.004Os0.003)∑1 or the simplified formula, (Ni,Fe,Ir). Garutiite is the Ni analogue of hexaferrum, osmium and ruthenium and is classified as belonging to the osmium Group. As such, the mineral is considered to be hexagonal, crystallizing in space Group P 63/ mmc with a 2.6941(4) and c 4.2731(6) A , V = 26.86(1) A 3, Z = 2. The strongest lines of the X-ray powder diffraction pattern [ d (in A )(I)( hkl )] are: 2.330(50)(100), 2.136(30)(002), 2.046(100)(101), 1.576(30)(102), 1.3470(40)(110), 1.2155(40)(103). Based on its morphology, internal texture, and the associated minerals, garutiite is interpreted to be secondary in origin, i.e ., having formed at low temperatures during post magmatic processes, such as serpentinization and/or lateritization. The name honors Prof. Giorgio Garuti, in recognition of his contributions to the understanding of the mineralogy of platinum-Group elements.

  • NIELSENITE, PdCu3, A NEW PLATINUM-Group INTERMETALLIC MINERAL SPECIES FROM THE SKAERGAARD INTRUSION, GREENLAND
    Canadian Mineralogist, 2008
    Co-Authors: Andrew M. Mcdonald, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Kirk C. Ross
    Abstract:

    Nielsenite, PdCu 3 , a new mineral species discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland, occurs in a tholeiitic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote-Group minerals, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules principally composed of bornite–chalcocite, chalcocite, along with rare digenite, chalcopyrite, cobaltpentlandite, Co-rich pentlandite, and sphalerite. Associated platinum-Group minerals include skaergaardite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au), (Pd,Cu,Sn) and (Pt,Fe,Cu,Pd) alloys and unnamed Au 3 Cu and PdAuCu. Nielsenite occurs as discrete grains or in sulfide-bearing, droplet-shaped to irregular grains that are 5–50 μm (ave: 16 μm) in size. The mineral is steel-grey in color with a metallic luster, a black streak and a sectile tenacity. No discernible forms or faces were observed. Neither cleavage nor fracture was observed, and no micro-indentation measurements were made. The mineral is non-pleochroic and exhibits neither discernible internal reflections nor evidence for twinning. It appears bright creamy white under reflected light. Reflectance values (in %) in air (in oil) are: 57.6 (47.5) at 470 nm, 60.85 (50.8) at 546 nm, 62.8 (53.0) at 589 nm and 66.7 (57.5) at 650 nm. The average result of 11 analyses is (in wt.%): Pd 29.86, Pt 3.08, Au 3.70, Cu 61.96, Fe 0.59, Pb 0.17, total 99.36%. The empirical formula (normalized to 4 apfu ) is: (Pd 0.862 Au 0.058 Pt 0.049 Fe 0.028 Pb 0.003 )(Cu 2.996 Fe 0.004 ) ∑3 or, ideally, PdCu 3 . The mineral is tetragonal, space Group P 4 mm , with a 3.7125(8), c 25.62(1) A, V 353.2(1) A 3 for Z = 4. The strongest six lines on the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 2.137(100)(117), 1.8596(70)(200), 1.8337(40)(0014), 1.3126(60)(220), 1.1188(55)(317), and 1.0663 (30)(2214). Nielsenite is considered to be isostructural with synthetic tetragonal PdCu 3 ( P 4 mm ). The mineral is commonly associated with skaergaardite (PdCu), which is considered to form at ~600°C under conditions of fairly high f (S 2 ) (>7 log units). Synthetic PdCu 3 forms at or below 508°C and is characterized by a relatively high degree of Pd–Cu disorder, consistent with observations made for nielsenite. The name honors Troels F.D. Nielsen, geologist with the Geological Survey of Denmark and Greenland.

Andrew M. Mcdonald - One of the best experts on this subject based on the ideXlab platform.

  • Skaergaardite, PdCu, a new platinum-Group intermetallic mineral from the Skaergaard intrusion, Greenland
    Mineralogical Magazine, 2020
    Co-Authors: N. S. Rudashevsky, Andrew M. Mcdonald, Louis J. Cabri, Chris J. Stanley, Troels F.d. Nielsen, Yu. L. Kretzer, V. N. Rudashevsky
    Abstract:

    Skaergaardite, PdCu, is a new mineral discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. It occurs in a tholeitiic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules composed of bornite, chalcocite, digenite, chalcopyrite, with rare cobalt pentlandite, cobaltoan pentlandite, sphalerite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au) and Pt-Fe-Cu-Pd alloys, unnamed PdCu3, (Pd,Cu,Sn), Au3Cu and PdAuCu. Skaergaardite occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and as irregular grains that vary in size from 2 to 75 mm, averaging 22 mm. It is steel grey with a bronze tint, has a black streak, a metallic lustre and is sectile. Neither cleavage nor fracture was observed. The mineral has a micro-indentation hardness of VHN25 = 257. It is isotropic, non-pleochroic and exhibits neither discernible internal reflections nor evidence of twinning. Skaergaardite varies from bright creamy white (associated with bornite and chalcopyrite) to bright white (associated with digenite and chalcocite). Reflectance values in air (and in oil) are: 58.65 (47.4) at 470 nm, 62.6 (51.1) at 546 nm, 64.1 (52.8) at 589 nm and 65.25 (53.95) at 650 nm. The average of 311 electron-microprobe analyses gives: Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28 and Pb 0.39, total 9 9.19 w t.%, c orresponding t o ( Pd 0.967 Au 0.020 Pt 0.010 )S 0.997 (Cu 0.820 Fe 0.120 Zn0.039Sn0.016Te0.004Pb0.003)S1.002. The mineral is cubic, space Group Pm3m, a = 3.0014(2) A ˚ , V = 27.0378 A ˚ 3 , Z =1 .Dcalc is 10.64 g/cm 3 . The six strongest lines in the X-ray powder-diffraction pattern [d inA ˚ (I)(hkl)] are: 2.122(100)(110), 1.5000(20)(200), 1.2254(50)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321). The mineral has the CsCl-type structure. It is believed to be isostructural with wairauite (CoFe), synthetic CuZn (b-brass) and is structurally related to hongshiite (PtCu). Skaergaardite developed from a disordered Pd-Cu-rich metal alloy melt that had exsolved from an earlier Cu-(Fe) sulphide melt. Ordering of Pd and Cu (beginning at T & 600oC) results in development of the CsCl structure from a disordered face-centred cubic structure.

  • Garutiite, (Ni,Fe,Ir), a new hexagonal polymorph of native Ni from Loma Peguera, Dominican Republic
    European Journal of Mineralogy, 2010
    Co-Authors: Andrew M. Mcdonald, Joaquín A. Proenza, Federica Zaccarini, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Joan Carles Melgarejo, John F. Lewis, Francisco Longo
    Abstract:

    Garutiite (Ni,Fe,Ir) is a new hexagonal polymorph of native Ni discovered in chromitite from Loma Peguera, Dominican Republic. The mineral was identified in heavy mineral concentrates obtained through the use of electric pulse disaggregation (EPD) and hydroseparation (HS) techniques. It forms as anhedral, botryoidal grains typically 10–60 μm in size (maximum of 110 μm). Grains are single or composite, frequently porous and zoned, and occasionally display an unusual lamellar internal texture. Associated minerals include hexaferrum, ferrian chromite, Chlorite-Group minerals, serpentine-Group minerals, awaruite, irarsite, laurite, native Ru and unidentified species including Ru–Os–Ir-Fe and Pt–Ni–Fe–Ir compounds, Pt(Ni,Fe)3, (Fe,Ru,Ni,Os,Ir,Co)2S and RhNiAs. The mineral is megascopically grey to grey-black with a metallic luster. In plane-polarized light, garutiite is white in color, exhibits a very weak anisotropy, and no pleochroism, bireflectance or internal reflections were observed. No cleavage was noted and the hardness could not be determined owing to the porous nature of the mineral. The calculated density is 11.33 (1) g/cm3. Reflectance values (%) in air are: 63.8 at 470, 65.9 at 546, 67.0 at 589 and 68.0 at 650 nm. The average result of electron microprobe analyses ( n = 42 from 27 grains) is: Ni 27.91, Fe 19.94, Ir 43.78, Pt 6.98, Co 0.55, Cu 0.43, Ru, 0.50, Rh 0.74, Os 0.67, total 101.51 wt%, corresponding to (Ni0.421Fe0.316Ir0.202Pt0.032Co0.008Cu0.006Rh0.006Ru0.004Os0.003)∑1 or the simplified formula, (Ni,Fe,Ir). Garutiite is the Ni analogue of hexaferrum, osmium and ruthenium and is classified as belonging to the osmium Group. As such, the mineral is considered to be hexagonal, crystallizing in space Group P 63/ mmc with a 2.6941(4) and c 4.2731(6) A , V = 26.86(1) A 3, Z = 2. The strongest lines of the X-ray powder diffraction pattern [ d (in A )(I)( hkl )] are: 2.330(50)(100), 2.136(30)(002), 2.046(100)(101), 1.576(30)(102), 1.3470(40)(110), 1.2155(40)(103). Based on its morphology, internal texture, and the associated minerals, garutiite is interpreted to be secondary in origin, i.e ., having formed at low temperatures during post magmatic processes, such as serpentinization and/or lateritization. The name honors Prof. Giorgio Garuti, in recognition of his contributions to the understanding of the mineralogy of platinum-Group elements.

  • NIELSENITE, PdCu3, A NEW PLATINUM-Group INTERMETALLIC MINERAL SPECIES FROM THE SKAERGAARD INTRUSION, GREENLAND
    Canadian Mineralogist, 2008
    Co-Authors: Andrew M. Mcdonald, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Kirk C. Ross
    Abstract:

    Nielsenite, PdCu 3 , a new mineral species discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland, occurs in a tholeiitic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote-Group minerals, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules principally composed of bornite–chalcocite, chalcocite, along with rare digenite, chalcopyrite, cobaltpentlandite, Co-rich pentlandite, and sphalerite. Associated platinum-Group minerals include skaergaardite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au), (Pd,Cu,Sn) and (Pt,Fe,Cu,Pd) alloys and unnamed Au 3 Cu and PdAuCu. Nielsenite occurs as discrete grains or in sulfide-bearing, droplet-shaped to irregular grains that are 5–50 μm (ave: 16 μm) in size. The mineral is steel-grey in color with a metallic luster, a black streak and a sectile tenacity. No discernible forms or faces were observed. Neither cleavage nor fracture was observed, and no micro-indentation measurements were made. The mineral is non-pleochroic and exhibits neither discernible internal reflections nor evidence for twinning. It appears bright creamy white under reflected light. Reflectance values (in %) in air (in oil) are: 57.6 (47.5) at 470 nm, 60.85 (50.8) at 546 nm, 62.8 (53.0) at 589 nm and 66.7 (57.5) at 650 nm. The average result of 11 analyses is (in wt.%): Pd 29.86, Pt 3.08, Au 3.70, Cu 61.96, Fe 0.59, Pb 0.17, total 99.36%. The empirical formula (normalized to 4 apfu ) is: (Pd 0.862 Au 0.058 Pt 0.049 Fe 0.028 Pb 0.003 )(Cu 2.996 Fe 0.004 ) ∑3 or, ideally, PdCu 3 . The mineral is tetragonal, space Group P 4 mm , with a 3.7125(8), c 25.62(1) A, V 353.2(1) A 3 for Z = 4. The strongest six lines on the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 2.137(100)(117), 1.8596(70)(200), 1.8337(40)(0014), 1.3126(60)(220), 1.1188(55)(317), and 1.0663 (30)(2214). Nielsenite is considered to be isostructural with synthetic tetragonal PdCu 3 ( P 4 mm ). The mineral is commonly associated with skaergaardite (PdCu), which is considered to form at ~600°C under conditions of fairly high f (S 2 ) (>7 log units). Synthetic PdCu 3 forms at or below 508°C and is characterized by a relatively high degree of Pd–Cu disorder, consistent with observations made for nielsenite. The name honors Troels F.D. Nielsen, geologist with the Geological Survey of Denmark and Greenland.

N. S. Rudashevsky - One of the best experts on this subject based on the ideXlab platform.

  • Skaergaardite, PdCu, a new platinum-Group intermetallic mineral from the Skaergaard intrusion, Greenland
    Mineralogical Magazine, 2020
    Co-Authors: N. S. Rudashevsky, Andrew M. Mcdonald, Louis J. Cabri, Chris J. Stanley, Troels F.d. Nielsen, Yu. L. Kretzer, V. N. Rudashevsky
    Abstract:

    Skaergaardite, PdCu, is a new mineral discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. It occurs in a tholeitiic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules composed of bornite, chalcocite, digenite, chalcopyrite, with rare cobalt pentlandite, cobaltoan pentlandite, sphalerite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au) and Pt-Fe-Cu-Pd alloys, unnamed PdCu3, (Pd,Cu,Sn), Au3Cu and PdAuCu. Skaergaardite occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and as irregular grains that vary in size from 2 to 75 mm, averaging 22 mm. It is steel grey with a bronze tint, has a black streak, a metallic lustre and is sectile. Neither cleavage nor fracture was observed. The mineral has a micro-indentation hardness of VHN25 = 257. It is isotropic, non-pleochroic and exhibits neither discernible internal reflections nor evidence of twinning. Skaergaardite varies from bright creamy white (associated with bornite and chalcopyrite) to bright white (associated with digenite and chalcocite). Reflectance values in air (and in oil) are: 58.65 (47.4) at 470 nm, 62.6 (51.1) at 546 nm, 64.1 (52.8) at 589 nm and 65.25 (53.95) at 650 nm. The average of 311 electron-microprobe analyses gives: Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28 and Pb 0.39, total 9 9.19 w t.%, c orresponding t o ( Pd 0.967 Au 0.020 Pt 0.010 )S 0.997 (Cu 0.820 Fe 0.120 Zn0.039Sn0.016Te0.004Pb0.003)S1.002. The mineral is cubic, space Group Pm3m, a = 3.0014(2) A ˚ , V = 27.0378 A ˚ 3 , Z =1 .Dcalc is 10.64 g/cm 3 . The six strongest lines in the X-ray powder-diffraction pattern [d inA ˚ (I)(hkl)] are: 2.122(100)(110), 1.5000(20)(200), 1.2254(50)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321). The mineral has the CsCl-type structure. It is believed to be isostructural with wairauite (CoFe), synthetic CuZn (b-brass) and is structurally related to hongshiite (PtCu). Skaergaardite developed from a disordered Pd-Cu-rich metal alloy melt that had exsolved from an earlier Cu-(Fe) sulphide melt. Ordering of Pd and Cu (beginning at T & 600oC) results in development of the CsCl structure from a disordered face-centred cubic structure.

  • Garutiite, (Ni,Fe,Ir), a new hexagonal polymorph of native Ni from Loma Peguera, Dominican Republic
    European Journal of Mineralogy, 2010
    Co-Authors: Andrew M. Mcdonald, Joaquín A. Proenza, Federica Zaccarini, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Joan Carles Melgarejo, John F. Lewis, Francisco Longo
    Abstract:

    Garutiite (Ni,Fe,Ir) is a new hexagonal polymorph of native Ni discovered in chromitite from Loma Peguera, Dominican Republic. The mineral was identified in heavy mineral concentrates obtained through the use of electric pulse disaggregation (EPD) and hydroseparation (HS) techniques. It forms as anhedral, botryoidal grains typically 10–60 μm in size (maximum of 110 μm). Grains are single or composite, frequently porous and zoned, and occasionally display an unusual lamellar internal texture. Associated minerals include hexaferrum, ferrian chromite, Chlorite-Group minerals, serpentine-Group minerals, awaruite, irarsite, laurite, native Ru and unidentified species including Ru–Os–Ir-Fe and Pt–Ni–Fe–Ir compounds, Pt(Ni,Fe)3, (Fe,Ru,Ni,Os,Ir,Co)2S and RhNiAs. The mineral is megascopically grey to grey-black with a metallic luster. In plane-polarized light, garutiite is white in color, exhibits a very weak anisotropy, and no pleochroism, bireflectance or internal reflections were observed. No cleavage was noted and the hardness could not be determined owing to the porous nature of the mineral. The calculated density is 11.33 (1) g/cm3. Reflectance values (%) in air are: 63.8 at 470, 65.9 at 546, 67.0 at 589 and 68.0 at 650 nm. The average result of electron microprobe analyses ( n = 42 from 27 grains) is: Ni 27.91, Fe 19.94, Ir 43.78, Pt 6.98, Co 0.55, Cu 0.43, Ru, 0.50, Rh 0.74, Os 0.67, total 101.51 wt%, corresponding to (Ni0.421Fe0.316Ir0.202Pt0.032Co0.008Cu0.006Rh0.006Ru0.004Os0.003)∑1 or the simplified formula, (Ni,Fe,Ir). Garutiite is the Ni analogue of hexaferrum, osmium and ruthenium and is classified as belonging to the osmium Group. As such, the mineral is considered to be hexagonal, crystallizing in space Group P 63/ mmc with a 2.6941(4) and c 4.2731(6) A , V = 26.86(1) A 3, Z = 2. The strongest lines of the X-ray powder diffraction pattern [ d (in A )(I)( hkl )] are: 2.330(50)(100), 2.136(30)(002), 2.046(100)(101), 1.576(30)(102), 1.3470(40)(110), 1.2155(40)(103). Based on its morphology, internal texture, and the associated minerals, garutiite is interpreted to be secondary in origin, i.e ., having formed at low temperatures during post magmatic processes, such as serpentinization and/or lateritization. The name honors Prof. Giorgio Garuti, in recognition of his contributions to the understanding of the mineralogy of platinum-Group elements.

  • NIELSENITE, PdCu3, A NEW PLATINUM-Group INTERMETALLIC MINERAL SPECIES FROM THE SKAERGAARD INTRUSION, GREENLAND
    Canadian Mineralogist, 2008
    Co-Authors: Andrew M. Mcdonald, N. S. Rudashevsky, Louis J. Cabri, Chris J. Stanley, V. N. Rudashevsky, Kirk C. Ross
    Abstract:

    Nielsenite, PdCu 3 , a new mineral species discovered in the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland, occurs in a tholeiitic gabbro associated with plagioclase, clinopyroxene, orthopyroxene, ilmenite, titanian magnetite, fayalite and accessory Chlorite-Group minerals, ferrosaponite, a member of the annite–phlogopite series, hornblende, actinolite, epidote-Group minerals, calcite, ankerite, apatite and baddeleyite. The mineral is found in composite microglobules principally composed of bornite–chalcocite, chalcocite, along with rare digenite, chalcopyrite, cobaltpentlandite, Co-rich pentlandite, and sphalerite. Associated platinum-Group minerals include skaergaardite, keithconnite, vasilite, zvyagintsevite, (Cu,Pd,Au), (Pd,Cu,Sn) and (Pt,Fe,Cu,Pd) alloys and unnamed Au 3 Cu and PdAuCu. Nielsenite occurs as discrete grains or in sulfide-bearing, droplet-shaped to irregular grains that are 5–50 μm (ave: 16 μm) in size. The mineral is steel-grey in color with a metallic luster, a black streak and a sectile tenacity. No discernible forms or faces were observed. Neither cleavage nor fracture was observed, and no micro-indentation measurements were made. The mineral is non-pleochroic and exhibits neither discernible internal reflections nor evidence for twinning. It appears bright creamy white under reflected light. Reflectance values (in %) in air (in oil) are: 57.6 (47.5) at 470 nm, 60.85 (50.8) at 546 nm, 62.8 (53.0) at 589 nm and 66.7 (57.5) at 650 nm. The average result of 11 analyses is (in wt.%): Pd 29.86, Pt 3.08, Au 3.70, Cu 61.96, Fe 0.59, Pb 0.17, total 99.36%. The empirical formula (normalized to 4 apfu ) is: (Pd 0.862 Au 0.058 Pt 0.049 Fe 0.028 Pb 0.003 )(Cu 2.996 Fe 0.004 ) ∑3 or, ideally, PdCu 3 . The mineral is tetragonal, space Group P 4 mm , with a 3.7125(8), c 25.62(1) A, V 353.2(1) A 3 for Z = 4. The strongest six lines on the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 2.137(100)(117), 1.8596(70)(200), 1.8337(40)(0014), 1.3126(60)(220), 1.1188(55)(317), and 1.0663 (30)(2214). Nielsenite is considered to be isostructural with synthetic tetragonal PdCu 3 ( P 4 mm ). The mineral is commonly associated with skaergaardite (PdCu), which is considered to form at ~600°C under conditions of fairly high f (S 2 ) (>7 log units). Synthetic PdCu 3 forms at or below 508°C and is characterized by a relatively high degree of Pd–Cu disorder, consistent with observations made for nielsenite. The name honors Troels F.D. Nielsen, geologist with the Geological Survey of Denmark and Greenland.

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  • heat pulse calorimetry measurements on natural Chlorite Group minerals
    American Mineralogist, 2007
    Co-Authors: Christian Bertoldi, Edgar Dachs, Peter Appel
    Abstract:

    Low- and high-temperature heat capacities of five natural Chlorite-Group samples were measured using the heat-capacity option of the Physical Properties Measurement System (Quantum Design), which is based on the principles of heat-pulse calorimetry, and by differential scanning calorimetry. Comprehensive chemical analyses were performed on these samples by electron microprobe analysis, by inductively coupled plasma mass spectrometry, and by Karl-Fischer titration (for H2O). The natural Chlorites span a range in X-Fe from 0.052 to 0.885 with increasing Al-content due to the Tschermak substitution with increasing X-Fe. The measured heat capacities were extrapolated to the end-member compositions of chamosite and clinochlore. Integration of heat-capacity data yields the calorimetric standard entropies of chamosite (Fe5Al)[Si3AlO10](OH)(8) and clinochlore (Mg5Al)[Si3AlO10](OH)(8), with values of 572.0 +/- 0.2 and 425.6 +/- 0.4 J/(mol-K), respectively. The C-p-polynomial for end-member chamosite is C-p = 1151.7 - 8.4564 x 10(3)-T-0.5 - 13.206 x 10(6)-T-2 + 15.233 x 10(8).T-3 [J/(mol-K)], valid in the temperature range of 298.15-900 K, and that for end-member clinochlore is C-p = 1160.5 - 9.9819 x 10(3)-T-0.5 - 5.9534 x 10(6).T-2 + 3.8677 x 10(8)-T-3 [J/(mol-K)], valid in the temperature range of 298.15-1000 K. The Fe-rich Chlorites exhibit an asymmetric distribution of the excess heat capacity in a plot of C-p(ex) vs. T, with a maximum at about 52 K. By analogy to annite, we interpret this peak to represent the magnetic ordering temperature. Based on our standard entropy value for chamosite, the enthalpy of formation of berthierine (Fe2.5Al0.5)[Si1.5Al0.5O5Y](OH)(4) was estimated as -3570.30 kJ/mol using a reported onset temperature of 70 degrees C at 16 MPa for the berthierine-chamosite polymorphic transition.

  • The Heat Capacity of the Serpentine SubGroup Mineral Berthierine (Fe_2.5Al_0.5)[Si_1.5Al_0.5O_5](OH)_4
    Clays and Clay Minerals, 2005
    Co-Authors: Christian Bertoldi, Edgar Dachs, Lado Cemic, Thomas Theye, Richard Wirth, Werner Groger
    Abstract:

    The serpentine subGroup mineral berthierine was synthesized as a metastable precursor of the Chlorite Group mineral chamosite in cold seal pressure vessels at 575°C, 0.5 GPa and f _O_2-conditions of the NNO buffer from a glass of almandine bulk composition. The run products were investigated with X-ray powder diffraction (XRD), Mossbauer spectroscopy and electron microprobe analysis. One run product was also investigated by high-resolution transmission electron microscopy (HRTEM) and its heat capacity measured by heat pulse calorimetry and by differential scanning calorimetry in the temperature range 5–323 K. The XRD and HRTEM investigations clearly showed that the periodicity along the c axis of this sample is 7 Å demonstrating that the serpentine subGroup mineral berthierine of composition (Fe^2+_1.83Fe^3+_0.33Al_0 67)[Si_1.33Al_0.67O_5](OH)_4 has formed in the synthesis experiments. Integration of our heat capacity data, corrected to the composition (Fe_2.5Al_0.5)[Si_1.5Al_0.5O_5](OH)_4 for end-member berthierine, yields a standard entropy of 284.1±0.3 J mol^−1 K^−1. The C _p polynomial C _p = 610.72 − 5140.0 × T ^−0.5 − 5.8848 × 10^6 T ^−2 + 9.5444 × 10^8 T ^–3 is recommended for thermodynamic calculations above 298 K involving berthierine.

  • The heat capacity of the serpentine subGroup mineral berthierine (Fe2.5Al0.5) Si1.5Al0.5O5 (OH)(4)
    Clays and Clay Minerals, 2005
    Co-Authors: Christian Bertoldi, Edgar Dachs, L Cemic, Thomas Theye, Richard Wirth, Werner Groger
    Abstract:

    The serpentine subGroup mineral berthierine was synthesized as a metastable precursor of the Chlorite Group mineral chamosite in cold seal pressure vessels at 575 degrees C, 0.5 GPa and f(O2) -conditions of the NNO buffer from a glass of almandine bulk composition. The run products were investigated with X-ray powder diffraction (XRD), Mossbauer spectroscopy and electron microprobe analysis. One run product was also investigated by high-resolution transmission electron microscopy (HRTEM) and its heat capacity measured by heat pulse calorimetry and by differential scanning calorimetry in the temperature range 5-323 K. TheXRD and HRTEM investigations clearly showed that the periodicity along the e axis of this sample is 7 A demonstrating that the serpentine subGroup mineral berthierine of composition (Fe1832+Fe0.333+Al0.67)-Fe-.)[Si1.33Al0.67O5](OH)(4) has formed in the synthesis experiments. Integration of our heat capacity data, corrected to the composition (Fe2.5Al0.5)[Si1.5Al0.5O5](OH)(4) for end-member berthicrine, yields a standard entropy of 284.1 +/- 0.3 J mol(-1) K-1. The C-p polynomial C-p = 610.72 - 5140.0 x T-0.5 - 5.8848 x 10(6) T-2 + 9,5444 x 10(8) T-3 is recommended for thermodynamic calculations above 298 K involving berthierine.

  • the heat capacity of two natural Chlorite Group minerals derived from differential scanning calorimetry
    Pacific Rim Conference on Multimedia, 2001
    Co-Authors: Christian Bertoldi, Artur Benisek, L Cemic, Edgar Dachs
    Abstract:

    The heat capacity of natural chamosite (X-Fe = 0.889) and clinochlore (X-Fe = 0.116) were measured by differential scanning calorimetry (DSC). The samples were characterised by X-ray diffraction, microprobe analysis and Mossbauer spectroscopy. DSC measurements between 143 and 623 K were made following the procedure of Bosenick et al. (1996). The fitted data for natural chamosite (CA) in J mol-l K-L give: C-p.CA = 1224.3-10.685 x 10(3) x T-0.5 - 6.4389 x 10(6) x T-2 + 8.0279 x 10(8) x T-3 and for the natural clinochlore (CE): C-p.CE 1200.5-10.908 X 10(3) x T-0.5 -5.6941 x 10(6) x T-2 + 7.1166 x 10(8) x T-3. The corrected C-p-polynomial for pure end-member chamosite (Fe5Al)[Si3AlO10](OH)(8) is C-p.CAcor = 1248.3-11.116 X 10(3) x T-0.5 - 5.1623 x 10(6) x T-2 + 7.1867 x 10(8) x T-3 and the corrected C-p-polynomial for pure end-member clinochlore (Mg5Al)[Si3AlO10](OH)(8) is C-p.CEcor = 1191.3-10.665 x 10(3) x T-0.5 -6.5136 X 10(6) X T-2 + 7.7206 x 10(8) x T-3. The corrected C-p-polynomial for clinochlore is in excellent agreement with that in the internally consistent data sets of Berman (1988) and Holland and Powell (1998). The derived C-p-polynomial for chamosite (Cp.CAcor) leads to a 4.4% higher heat capacity, at 300 K, compared to that estimated by Holland and Powell (1998) based on a summation method. The corrected C-p-polynomial (C-p.CAcor) is, however, in excellent agreement with the computed C-p-polynomial given by Saccocia and Seyfried (1993), thus supporting the reliability of Berman and Brown's (1985) estimation method of heat capacities.