File:Massive sulfide (bornite & Pt Pd-rich chalcopyrite-pyrrhotite) (platinum-palladium ore) (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) (14828837001).jpg
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editDescriptionMassive sulfide (bornite & Pt Pd-rich chalcopyrite-pyrrhotite) (platinum-palladium ore) (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) (14828837001).jpg |
Massive sulfide from the Precambrian of Montana, USA. (4.6 cm across at its widest) Southern Montana’s Beartooth Mountains has one of only three platinum mines in North America. There, platinum and palladium are mined from the 2.71 billion-year-old Stillwater Complex, a classic example of an LLI (large, layered igneous province). LLIs are large intrusive bodies that display large-scale and small-scale layering, even including cross bedding, ripples, graded bedding, channelforms, and other sedimentary-like features. The Stillwater started out as a large subsurface mass of slowly cooling magma. As various minerals crystallized, they settled to the bottom of the magma chamber. This resulted in layering. Igneous rocks that formed this way have a cumulate texture. Currents in the still-liquid portions of the magma chamber produced the sedimentary structures mentioned above. Most of the Stillwater displays only large-scale layering. The rocks in the Stillwater are ultramafic & mafic intrusive igneous rocks. Common lithologies include gabbros, norites, harzburgites, anorthosites, troctolites, chromitites, pyroxenites, and dunites. Portions of the Stillwater have been metamorphosed. Olivine is the most commonly altered component, usually metamorphosed to serpentine. The main platinum & palladium occurrence is in the Johns-Manville Reef (J-M Reef), an interval in the lower part of the Lower Banded Series. There, the Pt & Pd occur in intercumulate sulfides, typically pyrrhotite (Fe1-xS) and chalcopyrite (CuFeS2). Platinum ores in the J-M Reef are principally sulfidic anorthosites, but other lithologies also occur. The J-M Reef is the highest grade deposit known for platinum-group elements (PGEs). Platinum- and palladium-bearing pyrrhotite & chalcopyrite in the Stillwater Complex usually occur as intercumulate fills between crystals of plagioclase or pyroxene or olivine/serpentine. Occasionally, these sulfide minerals occur in a massive state. This is a fragment of massive sulfide from the Stillwater Complex’s J-M Reef. The yellowish-gold colored material is Pt/Pd-rich chalcopyrite, and the brownish-gold colored material is Pt/Pd-rich pyrrhotite. There are other minerals present, including bornite (Cu5FeS4) (dark, multicolored areas), and small patches of some silvery-colored mineral (what?). Several rare sulfide and element and element-alloy minerals have been reported from the Stillwater, including hollingworthite ((Rh,Pt,Pd)AsS), gold (Au), tetraferroplatinum (PtFe), palladobismutharsenide (Pd2(Bi,As)), braggite ((Pt,Pd,Ni)S), keithconnite (Pd3-xTe), moncheite (Pt(Te,Bi)2), vysotskite ((Pd,Ni)S), etc. Stratigraphy: Johns-Manville Reef, Lower Banded Series, Stillwater Complex, Neoarchean, 2.71 Ga Locality: 46W500 stope (4600’ elevation above sea level & 500’ west of shaft), Stillwater Mine, underground & west of the Stillwater River, southwestern Stillwater County, Beartooth Mountains, southern Montana, USA |
Date | |
Source | Massive sulfide (bornite & Pt/Pd-rich chalcopyrite-pyrrhotite) (platinum-palladium ore) (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14828837001 (archive). It was reviewed on 5 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
5 December 2019
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 05:44, 5 December 2019 | 2,632 × 1,807 (3.01 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Orientation | Normal |
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Horizontal resolution | 72 dpi |
Vertical resolution | 72 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 20:27, 4 August 2014 |
Color space | Uncalibrated |
Image width | 2,632 px |
Image height | 1,807 px |
Date and time of digitizing | 12:43, 10 February 2007 |
Date metadata was last modified | 16:27, 4 August 2014 |
IIM version | 2 |