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Can Mineral 2006;44:1513-1528.
TEXTURES AND COMPOSITIONAL VARIABILITY IN GERSDORFFITE FROM THE CRESCENCIA Ni–(Co–U) SHOWING, CENTRAL PYRENEES, SPAIN: PRIMARY DEPOSITION OR RE-EQUILIBRATION?
Isabel Fanlo, Ignacio Subías, Fernando Gervilla, and Jose Manuel
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FIG. 1. Representative textures of ore minerals from the Crescencia showing. All photomicrographs are back-scattered-electron images, except Figures 1C, D and E (reflected-light images). The numbers indicate sites of spot micro-analyses; the relevant compositions are presented in Tables 1 to 6. Symbols: Nc: nickeline; Gdf A to G: the seven different types of gersdorffite from stage II; Prr: pararammelsbergite, Py: pyrite, Urn: uraninite. (A) Anhedral aggregates of nickeline showing a cleavage (black areas) parallel to (0001) along which replacement has proceeded. (B) Euhedral crystals of gersdorffite A scattered in the masses of nickeline. (C) Crystals of gersdorffite A aligned along grain boundaries of nickeline. (D) Same photomicrograph as (C) under polarized light. (E) Growth and coalescence of gersdorffite A nuclei in nickeline masses. (F) Crystals of gersdorffite B showing complex twinning. (G) Nickeline crystals hosting minute inclusions of pararammelsbergite, partially replaced by gersdorffite C, which form rhythmically zoned reaction-rims. (H) Enlarged image of the left bottom of the Figure 2E showing the irregular distribution of the rims. (I) Irregular patches of gersdorffite E along the interface nickeline–gersdorffite; far from this recrystallization front, gersdorffite D is dominant. (J) Euhedral crystals of gersdorffite F marked by irregular growth-bands included in nickeline. (K) Euhedral crystal of gersdorffite G overgrows the pyrite grain disseminated in the black shale. (L) A recrystallization front of uraninite affecting both gersdorffite and nickeline. (M) The uraninite crystals occur as spheres and, locally, can be seen to grow along crystallographic directions in gersdorffite.

Can Mineral 2007;45:1147-1176.
MINERALOGY, MINERAL COMPOSITIONS AND FLUID EVOLUTION AT THE WENZEL HYDROTHERMAL DEPOSIT, SOUTHERN GERMANY: IMPLICATIONS FOR THE FORMATION OF KONGSBERG-TYPE SILVER DEPOSITS
Sebastian Staude, Thomas Wagner, and Gregor Markl
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FIG. 7. a. SEM–BSE image showing allargentum (Alg) partly replaced by native silver (Ag), and surrounded by "arite" and gersdorffite (Gdf). At the contact with allargentum, "arite" reacted to nickeline (Nc) and breithauptite (Bhp). Numbers refer to analyzed points shown in c and d. b. SEM–BSE image of "arite" and exsolved nickeline (Nc) and breithauptite (Bhp). Gersdorffite (Gdf) overgrows the "arite" aggregate. Ullmannite (Ull) probably formed later. Numbers refer to analyzed points shown in c and d. c. The analyzed points from a and b are plotted in the system Ni–Sb–As. "Arite" in contact with allargentum is enriched in Sb. d. Co appears to be incorporated preferentially into nickeline.

Can Mineral 2004;42:351-370.
Cu–Ni–PGE MINERALIZATION IN THE GENINA GHARBIA MAFIC–ULTRAMAFIC INTRUSION, EASTERN DESERT, EGYPT
Hassan M. Helmy
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FIG. 7. A) Brecciated pyrrhotite (Po), chalcopyrite (Ccp), nickeline (Nic) and cobaltite (inside the square) in a secondary silicate matrix along a small shear-zone, harzburgite, sample GG23. B) The cobaltite grain (in A) containing fine exsolution-induced domains of a Pd–Te phase (PdTe).

Can Mineral 2004;42:1221-1240.
THE COMPOSITION OF Co–Ni–Fe SULFARSENIDES, DIARSENIDES AND TRIARSENIDES FROM THE SAN JUAN DE PLAN DEPOSIT, CENTRAL PYRENEES, SPAIN
Isabel Fanlo, Ignacio Subías, Fernando Gervilla, Andrés Paniagua, and Belén García
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FIG. 2. Back-scattered electron images showing representative textures of the San Juan de Plan deposit. The numbers indicate compositions referenced in Tables 1 to 6. Symbols: Py I: pyrite from stage I; Apy: arsenopyrite; Nic: nickeline; Sk I: skutterudite from stage II; Sk II: skutterudite from stage V; Saf: safflorite; Ram: rammelsbergite; Allo: alloclasite; GC_ss I: gersdorffite–cobaltite solid-solution from stage III; GC_ss II: gersdorffite–cobaltite solid-solution from stage IV; As–Gdf: arsenic-rich gersdorffite; Cbt: cobaltite from stage VI. (A). Pyrite I (Py I) enclosed by GC_ss I and As–Gdf crystals. (B). Euhedral crystal of arsenopyrite (Apy) partially replaced by alloclasite (Allo). (C). Minute inclusion of nickeline (Nc) hosted by skutterudite I (Sk I), which, in turn, is overgrown by GC_ss II, showing complex zoning and growth history. The overgrowth is composed of As–Gdf. (D). Alloclasite (Allo) replaces skutterudite I (Sk I) showing rhomb-shaped crystals. (E). Skeletal masses of safflorite (Saf) being replaced by alloclasite (Allo) or GC_ss I. (F). Idiomorphic crystal of As–Gdf, partially replaced and overgrown by GC_ss II, which displays oscillatory growth-zonation. Both minerals are replaced by cobaltite (Cbt). (G). Idiomorphic crystals of GC_ss II showing very fine oscillatory growth-zonation, perfectly overgrown by As–Gdf, which shows irregular zonation; skutterudite II (Sk II) fills open spaces and partly replaces both minerals. (H). Irregular patches or lath-shaped crystal of GC_ss I overgrown by As–Gdf, which is, in turn, overgrown by GC_ss II. (I). Small crystals of rammelsbergite (Ram) and irregular masses of GC_ss I hosted by GC_ss II. Note that GC_ss II also fills cracks affecting GC_ss I. (J). Idiomorphic skutterudite II (Sk II) replaces or overgrows GC_ss II, As–Gdf and rammelsbergite (Ram), which can be seen as islands along the crystallographic directions. (K). NiK ${alpha}$ X-ray image of the top of the Figure 2J showing the location of As–Gdf and rammelsbergite crystals; the photomicrograph is rotated 30° with respect to Figure 2J.

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FIG. 3. (A) Back-scattered-electron images showing crystals of gersdorffite C. All the spot analyses are referenced in Table 3. (B) Enlarged image of a gersdorffite C crystal replacing nickeline (anal. 1 to 10, Table 3) and a small grain of pararammelsbergite (anal. 26 to 34). (C) Enlarged image to show the various reaction-fronts. The spot analyses located in the same rim and closest to pararammelsbergite (e.g., anal. 39 and 49) display similar compositions and are richer in As than those farther away from the core (e.g., anal. 43 and 54). (D) The reaction rims around the nickeline core are partially altered, which may be due to a re-equilibration of gersdorffite C, which leads to a S enrichment (cf. anal. 58 and 59).

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FIG. 8. a. Microphotograph of a polished section in air showing nickeline (Nc) replaced by a zoned aggregate of gersdorffite (Gdf) and rammelsbergite (Ram). Note that zoning in the Gdf–Ram aggregate continues into the skutterudite (Sk). b. This diagram shows the positive correlation between S and Co/(Co + Ni) in the triarsenides.

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FIG. 9. a. SEM–BSE image of Co–Ni-zoned gersdorffite (Gdf), which replaces nickeline (Nc). b. The Fe–Ni–Co plot of all sulfarsenides shows the nickel-rich composition of the Wenzel sulfarsenides. The lines are the solvus temperatures (°C) after Klemm (1965). Obviously, the mineral compositions do not reflect equilibrium values. See text for discussion.

Can Mineral 2005;43:899-908.
MINERALOGY OF THE NIEDERSCHLEMA–ALBERODA U – Se – POLYMETALLIC DEPOSIT, ERZGEBIRGE, GERMANY. V. WATKINSONITE, NEVSKITE, BOHDANOWICZITE AND OTHER BISMUTH MINERALS
Hans-Jürgen Förster, Gerhard Tischendorf, and Dieter Rhede
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FIG. 1. Back-scattered electron (BSE) and secondary electron (SE) images showing the texture and assemblage of Bi minerals from Niederschlema–Alberoda. a. BSE image of watkinsonite (dark) intergrown with clausthalite (bright) in sample Sh9. b. BSE image of watkinsonite associated with bohdanowiczite and clausthalite (Sh9). c. BSE image of nevskite rimming watkinsonite in clausthalite (Sh9). d. SE image of anhedral bohdanowiczite (dark) associated with clausthalite (bright) in sample R3. e. BSE image of bohdanowiczite and umangite replacing (?) eucairite in sample F2. f. SE image showing the assemblage native Bi + bismuthinite + nickeline + uraninite + coffinite in sample Sh76. g. SE image of native Bi replaced by bismuthinite and matildite (Sh76). Black areas represent gangue minerals.

10.

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FIG. 4. a. Hand specimen of allargentum showing the isometric granular grains on the broken surface. Field of view is about 4 cm. b. Photomicrograph of a polished section in oil showing the same fracture features. Symbols: Alg (allargentum), Ag (native silver). c. In hand specimen, dyscrasite (Dys) shows a well-developed cleavage and can be clearly distinguished from allargentum (Alg). Field of view is about 8 cm. d. Photomicrograph of a polished section of dyscrasite in oil, showing the same cleavage as in hand specimen. e. Photomicrograph of a polished section in oil showing allargentum (Alg) with exsolved native silver (Ag-I), late-stage native silver (Ag-II), nickeline (Nc) and gersdorffite (Gdf). f. This photomicrograph of a polished section in oil shows the relative age of formation of the late-stage native silver (Ag). Allargentum (Alg) was overgrown by gersdorffite (Gdf), and then galena (Gn) overgrew gersdorffite and replaced allargentum. After this mineralization, native silver replaced allargentum and surrounded galena. Two phases of replacement can be distinguished on the basis of the Sb content of the silver (Ag₉₅: native silver with 5 wt.% Sb; Ag₉₁: native silver with 9 wt.% Sb).

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