MINERALOGICAL JOURNAL, VOL. 6, No. 5, pp. 313-322, SEPT., 1971 PENTLANDITE, NICCOLITE AND GERSDORFFITE FROM THE HAN DERESI AND GUNES DISTRICTS, NEAR DIVRIGI, SIVAS, EASTERN TURKEY* KAZUO HARADA and YOSUKE TAGAWA Central Research Laboratory, Sumitomo Metal Mining Company, Ichikawa, Chiba, Japan KOZO NAGASHIMA and KAZUSO NAKAO Department of Chemistry, Faculty of Science, Tokyo University of Education, Otsuka, Tokyo, Japan and NOBORU TSUKAHARA Exploration Department, Sumitomo Metal Mining Company, 11-3, Shimbashi 5-chome, Minato-ku, Tokyo, Japan ABSTRACT Pentlandite, niccolite and gersdorffite from the Han Deresi and Giines districts, eastern Turkey, were described. The specific gravity and the cell constants of each of these specimens were measured, and it was con firmed that these physical data were in good agreement with those given in literatures. It was also concluded that the specimen of gersdorffite under investigation was of the ordered structure with the space group, P213-T4. Chemical analyses of these specimens were carried out both by the usual wet method and with a electron microprobe. The results indicated that, when gersdorffite and niccolite co-exist, Sb seems to prefer entering into gersdorffite to going into niccolite. The stability field of gesdorffite was discussed and it was inferred that the presence of Fe in place of Ni might widen the stability field of the ordered form. * Mineralogical Contribution No . 5., Central Research Laboratory of the Sumitomo Metal Mining Company. 314 Pentlandite, Niccolite and Gersdorffite from Introduction and specimens Pentlandite, niccolite and gersdorffite were collected by Noboru Tsukahara from the Han Deresi and Gunes districts, near Divrigi, Sivas, eastern Turkey. This study presents mineralogical descrip tions of these Ni minerals. All the specimens used are deposited in the Central Research Laboratory, Sumitomo Metal Mining Com pany, Ichikawa, Chiba, 272 Japan. Pentlandite (No. 51113). This mineral was found in the Han Deresi district as lenticular ore-bodies at a contact zone between serpentinite and gabbroic rocks of unknown geologic age and about 30 to 40cm in thickness and 5 to 10m in length. Under the microscope the sulfide phase consisted only of pure pentlandite with a minor amount of tremolite as a gangue mineral. The material, hand-picked and 20 gr. in weight, was used for the mineralogical studies. Niccolite and gersdorffite (Nos. 50802 and 51003). Both specimens were collected at Kurtbeyaz, Gunes near Divrigi. The specimens were found in a liparite dyke of unknown geologic age and as a hydrothermal veinlet of 6 to 10cm in width and 50m Fig. 1. Gersdorffite-niccolite-dolomite vein in a liparite dyke in the Gunes district, near Divrigi . K. HARADA, et al. 315 Fig. 2. Ore-micrograph of niccolite and gersdorffite. Niccolite (N) is surrounded by gersdorffite (G) in dolomite (D). in length (Fig. 1). The vein consists mainly of dolomite with small amounts of niccolite and gersdorffite. Under the microscope nic colite was always surronded by gersdorffite and neither anisotropism nor zoning was found in the gersdorffite as shown in Fig. 2. Hand picked specimens of niccolite and gersdorffite were used for the following mineralogical studies. Mineralogy Physical and X-ray data. The specific gravities determined with a 1ml pycnometer, and the unit cell constants derived from the X-ray powder patterns using CoKƒ¿1(ƒÉ=1.7889 A) radiation and silicon and silver metals as internal standards are summarized for these three minerals in Table 1. The cell constants obtained for each of these minerals were in good agreement with its data previously published, and other physical data were also found to agree with those expected for these species. However, it may be worthwhile to go into some details about the 316 Pentlacdite, Niccolite and Gersdorffite from Table 1. Unit cell edges and specific gravity of pentlandite, gersdorffite and niccolite. Note: Gersdorffite and niccolite under the same specimen number have been taken from the same hand specimen. X-ray data as follows. The cell constants of the present pentlandite fit well to the data of natural pentlandite given by Knop et al. (1961 and 1965). The specimens of gersdorffite (Nos. 50802 and 51003) show the 4.04A reflection (hkl=011) which indicates the ordered form with the space group P213-T4 (Bayliss, 1968). The X-ray powder diffrac tion peaks of gersdorffite are almost identical to the previous data (ASTM card No. 12-705; Berry & Tompson, 1962). A few of addi tional peaks observed in the present study but not mentioned in these previous reports are also compatible with P213-T4. The X ray powder data of this gersdorffite are given in Table 2. Chemical data Electronn microprobe analysis. Analyses of niccolite (No. 51003) and gersdorffite (No. 51003)were carried out with the Shimazu-ARL EMX I electron microprobe (accelerating voltage, 30 KV, sample K. HARADA, et al. 317 Table 2. X-ray powder diffraction data of gersdorffite. Notes: CoKƒ¿, radiation with Fe filter, ƒÉ=1.78890A; 30 KV, 10 mA. * Peaks not described in the ASTM card No . 12-705 and in the data by Berry and Thompson (1962). 318 Pentlandite, Niccolite and Gersdorffite. tom Table 3. Chemical analysis of gersdorffite, niccolite and pentlandite. Notes: (1) Gersdorffite (No. 51003) (2) Niccolite (No. 51003) (3) Gersdorffite (No. 50802) (4) Niccolite (No. 50802) (5) Pentlandite (No. 51113) * Electron microprobe analysis ** Wet chemical analysis *** Qualitative analysis with the Shimazu GE 340 grat ing-type spectrograph. The niccolite (No. 50802) was contaminated with small amounts of gersdorfflte. Thus, the structural formula of the niccolite was derived after reduction of gersdorffite as NiAsS to give; (Ni1.010, Co0.004, Fe0.005)1.019 As1.000. current, 0.05 ƒÊA; beam spot, 2ƒÊ). Corrections were made for mass absorption, fluorescence, and atomic numbers, and the results are given in Table 3 and Figs. 3 and 4. For analyses of Ni, Fe and Sb pure Ni, Fe and Sb metals were used as standards. Arsenopyrite and galena from the Chichibu mine, whose compositions had been confirmed by wet chemical analyses, were also used as the standards for As and S respectively. Structural formulae of the minerals are: for gersdorffite (No. 51003); •@(Fe0.014, Ni0..982) 0.996 (As0.990, Sb0.018)1.008S1.000, K. HARADA, et al. 319 Fig. 3. Electron-beam scanning image (E. B. S. image) of gersdorffite (G), niccolite (N), dolomite (D) and an unknown Fe-Ni-As-S bearing phase (X). 1, Sample current image (S. C. image); 2, Sb Lƒ¿l; 3, FeKƒ¿l and ƒ¿2; 4, NiKƒ¿l and ƒ¿2; 5, AsKƒ¿l and ƒ¿2; 6, SKƒ¿1 and ƒ¿2. 320 Pentlandite, Niccolite and Gersdorffite from Fig. 4. Line scanning figure of nicccolite and gersdorffite. G, gers dorffite; N, niccolite; D, dolomite. No compositional zonning was observed in the single grains of gersdorffite and niccolite. and for niccolite (No. 51003); Ni0.986(AS0.996, Sb0.004)1.000• These data are in agreement with the ideal compositions of the minerals. No compositional zonings were found within the single grains of gersdorffite and niccolite as will be seen in Fig. 4. An unknown phase (X), steely-grey in color with slightly yellowish tint under the microscope and containing Fe, Ni, As and S, was found along the rim of gersdorffite (No. 51003). However, the crystallo graphic study of the mineral has been deferred because of its very small grain-size (Fig. 3). Wet chemical analyses. Chemical analyses were carried by Na gashima and Nakao on several grammes of hand-picked materials and applying the following procedures. Sulfer: The sample was burned in a current of air in a combustion tube heated at 1000•Ž. Sulfer dioxide then formed was absorbed by hydrogen peroxide solution, and H2SO4 formed was subjected to titration with the standard sodium hydroxide solution. Arsenic: The sample was dis K. HARADA, et ai. 321 solved in aqua regia and after the separation by distillation from hydrochloric acid solution, arsenic (III) was subjected to titration with the standard iodine solution. Antimony: After separated as antimony (III) sulfide, the precipitate was dissolved in sodium hydro xide solution. The solution was treated with sulfuric acid and hy drochloric acid. Iron, nickel and cobalt: The sample was dissolved in nitric acid and treated several times with hydrochloric acid. Then the hydrochloric acid solution was divided into the iron, cobalt and nickel fractions using a strongly basic anion-exchange resin. Then iron was determined volumetrically by the ordinally perman ganate method. Cobalt and nickel were determined gravimetrically using ƒ¿-nitroso -ƒÀ naphtol and dimethylglyoxime, respectively. For the samples of low iron content, the direct spectrophotometric pro cedure with orthophenanthlovine was applied. The results are listed in Table 3. Recast in terms of structural formulae, these correspond to; Pentlandite (No. 51113); (Ni5.439, Fe3.558, Co0.069)9.066 S8.000, gersdorffite (No. 50802); (Fe0.035, Co0.006, Ni0.959)1.000 (As1.076, Sb0.007)1.083 S0.947, and niccolite (No. 50802); (Ni1,010,Co0.004, Fe0.005)1.019AS1.000. These data agree well each to the ideal formula of each mineral. It is to be noted that both specimens of gersdorffite (Nos. 51003 and 50802) contain a small amount of Fe substituting for Ni as well as Sb for As. In case of co-existence of gersdorffite and niccolite (No. 51003), Sb seems to enter more easily to the gersdorffite lattice than to the niccolite lattice because gersdorffite in the specimen contains 1.37-0.54% of Sb while niccolite contains 0.41% or less of Sb. Temperature of formation of gersdorffite-discussion According to the X-ray powder data of gersdorffite (Nos. 50802 and 51003), the mineral is of the ordered form with the space group 322 Pentlandite, Niccolite and Gersdorffite from P213-T4.