John L. Jambor

New mineral names

Alfredopetrovite (IMA 2015-026), ideally Al2(SeO3)3·6H2O, is a new selenite mineral from the El Dragόn mine, Antonio Quijarro Province, Potosí Department, Bolivia. The mine exploited a telethermal deposit consisting of a single selenide vein hosted by sandstones and shales. The main primary mineral is a Co-rich krut’aite–penroseite. Clausthalite, petrovicite, watkinsonite, eldragόnite, and grundmannite were crystallized from later solutions. Alfredopetrovite is a secondary mineral and occurs in vugs in a krut’aite-penroseite-dolomite-goethite matrix. Other closely associated secondary minerals are: ahlfeldite, allophane, calcite, chalcomenite, favreauite, felsőbányaite, malachite, and molybdomenite. Alfredopetrovite forms colorless to blue (transmit chalcomenite color) drusy/scaly coatings and compact balls up to 0.5 mm. Individual crystals are up to ~0.1 mm. Crystals are transparent with a white streak and a vitreous luster. The mineral is brittle with a smooth curved fracture and no apparent cleavage. Mohs hardness is 21⁄2. The density was not measured because crystal fragments are virtually invisible in density liquids; Dcalc = 2.504 g/cm3. Alfredopetrovite is optically uniaxial (+), ω = 1.554(2), and ε = 1.566(2) (white light); non-pleochroic. The average of 3 electron probe WDS analyses [wt% (range)/wt% normalized to 100%] is: CuO 1.27 (1.04–1.46)/1.09, CoO 0.12 (0.10–0.15)/0.10, NiO 0.51 (0.35–0.68)/0.44, Al2O3 20.99 (20.41–22.04)/18.12, SeO2 69.63 (68.83–70.36)/60.12, H2O (by structure analysis) 23.30/20.12, total 115.82/99.99. The high total is due to dehydration in vacuum and under electron beam. The empirical formula based on 15 O apfu is Al1.94Cu0.07Ni0.03Co0.01Se2.95O15H12.16. IR data was not obtained. The strongest lines in the X-ray powder diffraction pattern are [d Å (I; hkl)]: 7.63 (55; 100), 6.22 (55; 101), 5.37 (26; 002), 4.398 (40; 110,102), 3.404 (100; 112), 2.783 (50; 211), 2.606 (22; 203), 1.661 (26; 410,322,314,116). The unit-cell parameters refined from the powder data are: a = 8.7978(14), c = 10.7184(18) Å, V = 718.5 Å3. Alfredopetrovite is hexagonal, space group P62c. The single crystal unit-cell parameters are: a = 8.818(3), c = 10.721(2) Å, V = 722.0 Å3, and Z = 2. The crystal structure was refined to R1 = 0.0268 for 240 observed [Fo > 4σFo] reflections. The structure is comprised of fairly regular AlO6 octahedra and SeO3 triangular pyramids. Three SeO3 pyramids link two adjacent AlO6 octahedra forming a [Al(H2O)3]2(SeO3)3 unit. These units are bonded only via hydrogen bonds yielding a structure with relatively large channels along [001]. The configuration of the cluster is similar to that of the distinctive unit in the NASICON (sodium super-ionic conductor) structure, commonly referred as a lantern unit. The mineral is named in honor of Alfredo Petrov (b. 1955), geologist/mineralogist and an avid mineral collector for his contributions to mineralogy and geology of Bolivia and as well for his contributions to mineral collector’s community as an author of a numerous publications and an active manager of http://www.mindat.org. Four cotypes (one of those is also cotype for favreauite) are deposited in the Natural History Museum of Los Angeles County, Los Angeles, U.S.A. One cotype specimen (it is also a cotype of favreauite) is housed in the Museum Victoria, Australia. D.B.

The pore-water geochemistry and the mineralogy of the vadose zone of sulfide tailings, Waite Amulet, Quebec, Canada

Low-pH waters, requiring treatment because of high concentrations of dissolved metals, are being discharged from a decommissioned tailings impoundment at the former Waite Amulet ZnCu mine in northeastern Quebec, Canada. A detailed study of the vadose zone of the tailings comparing mineralogical and geochemical analyses of the tailings solids with geochemical analysis of the tailings pore water and pore gas indicates the presence of three zones within the tailings. These zones include an upper sulfide-depleted zone in which the sulfides have been extensively removed and oxidation is largely complete, an intermediate zone, where sulfide oxidation and acid neutralization reactions are occurring, and an unoxidized zone below the depth of oxygen penetration, where sulfides are unoxidized. High aqueous concentrations of dissolved solids are being displaced downward from the sulfide-depleted zone, through the unoxidized zone toward the water table. Sulfide-oxidation and acid-neutralization reactions have generated concentrations of dissolved solids high enough to lead to the precipitation of a series of secondary solid phases. Precipitation-dissolution reactions involving these solid phases control the concentrations of the major ions in the tailings pore water. Concentrations of dissolved metals are controlled by precipitation-dissolution, crystal-structural replacement, and adsorption/coprecipitation reactions. Predictions based on the observed data and numerical simulations suggest that, in the absence of an effective remedial program, sulfide oxidation and H+ production will continue for several centuries.

The formation and potential importance of cemented layers in inactive sulfide mine tailings

Abstract Investigations of inactive sulfide-rich tailings impoundments at the Heath Steele (New Brunswick) and Waite Amulet (Quebec) minesites have revealed two distinct types of cemented layers or “hardpans.” That at Heath Steele is 10–15 cm thick, occurs 20–30 cm below the depth of active oxidation, is continuous throughout the tailings impoundment, and is characterized by cementation of tailings by gypsum and Fe(II) solid phases, principally melanterite. Hardpan at the Waite Amulet site is only 1–5 cm thick, is laterally discontinuous (10–100 cm), occurs at the depth of active oxidation, and is characterized by cementation of tailings by Fe(III) minerals, principally goethite, lepidocrocite, ferrihydrite, and jarosite. At Heath Steele, an accumulation of gas-phase CO2, of up to 60% of the pore gas, occurs below the hardpan. The calculated diffusivity of the hardpan layer is only about 1 100 that of the overlying, uncemented tailings. The pore-water chemistry at Heath Steele has changed little over a 10-year period, suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation. Generation of a cemented layer therefore has significant environmental and economic implications. It is likely that, in sulfide-rich tailings impoundments, the addition of carbonate-rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers.

The potential for metal release by reductive dissolution of weathered mine tailings

Abstract Remediation programs proposed for decommissioned sulphide tailings may include the addition of a cover layer rich in organic-carbon material such as sewage sludge or composted municipal waste. These covers are designed to consume oxygen and prevent the oxidation of underlying sulphide minerals. The aerobic and anaerobic degradation of such organic-carbon-rich waste can release soluble organic compounds to infiltrating precipitation water. In laboratory experiments, and in natural settings, biotic and abiotic interactions between similar dissolved organic compounds and ferric-bearing secondary minerals have been observed to result in the reductive dissolution of ferric (oxy)hydroxides and the release of ferrous iron to pore waters. In weathered tailings, oxidation of sulphide minerals typically results in the formation of abundant ferric-bearing secondary precipitates near the tailings surface. These secondary precipitates may contain high concentrations of potentially toxic metals, either coprecipitated with or adsorbed onto ferric (oxy)hydroxides. Reductive dissolution reactions, resulting from the addition of the organic-carbon covers, may remobilize metals previously attenuated near the tailings surface. To assess the potential for metal release to tailings pore water by reductive dissolution reactions, a laboratory study was conducted on weathered tailings collected from the Nickel Rim mine tailings impoundment near Sudbury, Ontario, Canada. This site was selected for study because it is representative of many tailings sites. Mineralogical study indicates that sulphide minerals originally present in the vadose zone at the time of tailings deposition have been replaced by a series of secondary precipitates. The most abundant secondary minerals are goethite, gypsum and jarosite. Scanning electron microscopy, coupled with elemental analyses by X-ray energy dispersion analysis, and electron microprobe analysis indicate that trace metals including Ni, Cr and Cu are associated with these secondary minerals. To assess the masses of trace metals associated with each of the dominant secondary mineral phases, a series of extraction procedures was used. The masses of metals determined in three fractions (water soluble, reducible and residual) suggest that the greatest accumulation of metals is in the reducible fraction. These measurements indicate that high concentrations of metals are potentially available for release by reductive dissolution of the ferric-bearing secondary minerals. The actual mass of metals that can be released by this mechanism will depend on a number of site-specific characteristics, particularly the intensity of the reducing conditions established near the tailings surface.

The hydrogeochemistry of the Nickel Rim mine tailings impoundment, Sudbury, Ontario

From 1953 to 1958, mine tailings were deposited in an elevated impoundment at the Nickel Rim mine, an abandoned Ni–Cu mine near Sudbury, Ontario. The oxidation of sulfide minerals, principally pyrrhotite (8 wt.% of tailings), has generated low-pH waters and released high concentrations of Fe (up to 9.8 g/l), SO4 (up to 24 g/l), dissolved metals (1130 mg/l Al; 698 mg/l Ni) and other dissolved constituents. Groundwater flow through the tailings is mainly horizontal with velocities of 4–8 m/yr. Iron, SO4 and Mn are moving at groundwater velocities and a low-pH front (pH≤4.5) is moving more slowly than the groundwater velocity. A series of pH zones with pH values of 3.0, 4.1, 5.6 and 6.7 is present within the impoundment. The occurrence of these zones is attributed to the successive dissolution of iron (oxy)hydroxides, aluminum hydroxide and aluminosilicates, siderite and calcite. Concentrations of dissolved metals, including Al, Co, Cr, Ni and Zn are controlled by the pore-water pH, except for Cu, which is controlled by the precipitation of covellite. The dominant secondary minerals are goethite, jarosite and gypsum. Accumulations of gypsum and jarosite in the oxidation zone have been great enough to cement the tailings. The cemented layers limit O2 diffusion, resulting in longer oxidation times for the tailings. High concentrations of Fe and SO4 presently in the tailings pore-water will discharge from the impoundment for at least 50 years.

The solid-phase controls on the mobility of heavy metals at the Copper Cliff tailings area, Sudbury, Ontario, Canada

Abstract The Copper Cliff Tailings Disposal Area, located near Sudbury, Ontario, covers an area of approximately 2200 ha and constitutes more than 10% of the total area of all mine tailings in Canada. The area has been utilized since 1936, receiving sulphide-containing tailings from the Inco Sudbury operations. Field measurements of pore-gas oxygen and carbon dioxide in the vadose zone indicate that sulphide oxidation has progressed to depths of 1.6 m to 1.7 m within the tailings. The oxidation of sulphide minerals within the vadose zone, and the accompanying dissolution of carbonate and aluminosilicate minerals within these tailings releases SO 4 , Fe(II) and other metals to the pore water. In the vadose and saturated zones, concentrations of Fe and Ni exceed 10100 mg/l and 2210 mg/l, respectively. These high concentrations of dissolved metals are attenuated by a series of precipitation, coprecipitation and adsorption reactions. The precipitation of secondary sulphate and hydroxide phases also create hardpan layers at or near the oxidation front. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary-phase precipitation is occurring at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of jarosite, gypsum and goethite within the shallow tailings, suggesting that these phases are controlling the dissolved concentrations of Fe, SO 4 and Ca. Extraction experiments conducted on the tailings solids indicate that the constituents contained in the water-soluble fraction of the shallow, weathered tailings are derived from the original pore water and the dissolution of highly soluble phases such as gypsum. The acid-leachable fraction of the weathered tailings accounts for up to 25% of the heavy metals, and the reducible fraction may contain up to 100% of the heavy metals within the shallow, weathered tailings. Based on the pore water profiles and the geochemistry of the tailings solids, a relative mobility scale of Fe=Mn=Ni=Co>Cd Zn>Cr=Pb>Cu can be determined.

Aqueous geochemistry and analysis of pyrite surfaces in sulfide-rich mine tailings

Abstract Aqueous geochemical techniques and analysis of pyrite surfaces have been used to study element partitioning between the aqueous and solid phase and to infer mechanisms that limit the concentrations of elements in porewater in a sulfide-rich mine tailings impoundment. Porewater samples and pyrite grains for surface analysis were collected from oxidized and unoxidized zones within the tailings. Surface analyses were conducted using a Time-of-Flight Laser-Ionization Mass Spectrometer (TOFLIMS). The porewater pH at the different sample locations varies from 3.85 to 6.98. High relative abundances of Na, K, Ca, Mg, Al, and Ni occur at the surfaces of the pyrite grains from all of the sample locations. The porewater concentrations of these elements in the low-pH zone may be controlled by precipitation or coprecipitation in secondary mineral coatings on the pyrite surface. Surface abundances of the metals Cu, Ag, Pb, Zn, and Cd are lowest, and porewater concentrations are highest, in the low-pH oxidized tailings. Surface abundances of As are greatest, and porewater concentrations are lowest, in the low-pH sulfide-oxidation zone. These trends vs. pH are consistent with an adsorption model for attenuation of Cu, Ag, Pb, Zn, Cd, and As from the porewater. The porewater Cu and Ag concentrations may be limited by replacement reactions that form secondary Cu and Ag sulfides at the pyrite surface. The highest abundance of C on the surface of the pyrite grains is in the shallow sulfide-oxidation zone; this interval coincides with large abundances of chemolithotrophic bacteria and may reflect populations of iron- and sulfur-oxidizing bacteria such as Thiobacilli.

Microbiological, chemical, and mineralogical characterization of the kidd creek mine tailings impoundment, Timmins area, Ontario

Bacterial enumeration and geochemical characterization were undertaken at three sites on the sulfide‐rich tailings impoundment at the Kidd Creek metallurgical site, Timmins, Ontario, Canada. The three sites were selected to represent varying degrees of sulfide oxidation to assess the changes in water chemistry, in the mineralogical composition of the tailings, and in bacterial populations as the sulfide oxidation process proceeds under natural field conditions. The first site was characterized as having negligible oxidation‐derived alteration, the pH of the porewater varied from 6.5 to 7.5, and the concentrations of dissolved constituents were similar to those observed in the deeper, unaltered tailings. Mineralogical examination of the tailings grains indicated that the sulfide surfaces were sharp and unreplaced. At this site, the predominant sulfur‐oxidizing bacteria were Thiobacillus thioparus and related species. The second site showed evidence of the onset of acidification, the pH of the near‐surface ...

COMPARISON OF MEASURED AND MINERALOGICALLY PREDICTED VALUES OF THE SOBEK NEUTRALIZATION POTENTIAL FOR INTRUSIVE ROCKS 1

Twelve specimens of intrusive rocks, ranging from granitic to ultramafic, were ground and subjected to the static-test neutralization-potential (NP) protocol so that the results could be compared with those computed by using the NP values previously obtained by Sobek tests of the constituent minerals. The quantitative mineralogy of the rocks was determined by Rietveld refinements of X-ray powder diffraction data, and was supplemented by optical microscopy, fizz tests, and analyses of total carbon to determine the presence of carbonate minerals. Despite the igneous nature of the suite, most samples were found to be carbonate-bearing; optical microscopy and fizz tests of the coarse (minus 6 mm) fractions were observed to be more sensitive to the presence of carbonates than was the minus 60-mesh fraction that is used in the Sobek protocol. For some minerals, notably olivine and serpentine, the acid-digestion period in the Sobek test has a pronounced effect on the resulting NP, and this part of the test protocol is in need of new standardization. Mineralogical prediction of the NP values is sensitive to the composition of the plagioclase because these feldspars are typically a major component of igneous rocks and the NP of the calcic end- member, anorthite, is about 12 times that of the sodic end-member, albite.