File:Kimberlite-wall rock sample (Gates-Adah Kimberlite Dike, Early Jurassic; Fayette County, Pennsylvania, USA) (31547573652).jpg
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Kimberlite-wall rock sample from Pennsylvania, USA. (~11.2 centimeters across at its widest) Kimberlites and lamproites have tremendous economic importance because they are host rocks for gem-grade and industrial-grade diamonds. Kimberlites & lamproites are unusual igneous bodies having overall pipe-shaped geometries. Their mode of formation is only moderately understood because they have not been observed forming. Kimberlites & lamproites are known from scattered localities throughout the world - only some are significantly diamondiferous. Classic localities for diamonds are India and Brazil. Africa was also discovered to have many kimberlites and is world-famous for producing large numbers of diamonds. Other notable diamondiferous kimberlite-lamproite occurrences include Russia, China, northwestern Australia, and northwestern Canada. Kimberlites are named for the town of Kimberley, South Africa. Several kimberlite pipes occur in the Kimberley area. Kimberlites have a gently tapering-downward, pipe-shaped cross-section. Lamproites have a cross-section more closely resembling that of a martini glass. The rock seen here is from a non-diamondiferous kimberlite intrusion in Pennsylvania. Unlike most kimberlites, which have pipe-shaped geometries, this occurrence is an igneous dike. This sample has the actual dike-host rock contact. The lower half of the sample is the kimberlite, which has a groundmass consisting of olivine, phlogopite mica, and opaque minerals. Phenocrysts and megacrysts reported from the kimberlite include olivine (serpentinized) and pyrope garnet. The upper half of the sample is wall rock consisting of limestone from the Monongahela Group (Pennsylvanian in age) or the Waynesburg Formation (Pennsylvanian/Permian in age). Geologic unit: Gates-Adah Kimberlite Dike, middle Early Jurassic, 185 Ma Locality: Gates-Adah Kimberlite Dike trend, near Middle Run, east of the Monongahela River, north or northeast of the town of Gates, far-western Fayette County, southwestern Pennsylvania, USA Info. at: <a href="https://www.mindat.org/loc-52104.html" rel="noreferrer nofollow">www.mindat.org/loc-52104.html</a> |
| Date | |
| Source | Kimberlite-wall rock sample (Gates-Adah Kimberlite Dike, Early Jurassic; Fayette County, Pennsylvania, 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@N05/31547573652 (archive). It was reviewed on 6 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 04:01, 6 December 2019 | | 3,095 × 2,774 (6.39 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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