File:Phlogopite leucite lamproite lava (Ellendale Center No. 5, Lower Miocene, 19-22 Ma; Ellendale Lamproite Field, northeastern Canning Basin, northern Western Australia) 1 (15034287211).jpg
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| Description |
Phlogopite leucite lamproite lava from the Miocene of Australia (field of view ~7.5 cm across). 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. Western Australia's Ellendale Lamproite Field contains diamondiferous lamproite intrusions. Interestingly, lamproite lava (= extrusive lamproite) is associated with some of the Ellendale lamproite bodies. Lamproite lava is a rare rock type (ordinary intrusive lamproite pipes themselves are also rare). The rock shown here is a lamproite lava sample that's gorgeous in a way that the photo can't convey. The unweathered matrix is light gray-brown, and the large phenocrysts (black-looking or dark brown-looking or sparkly white in the photos below) are intensely lustrous golden-brown phlogopite mica crystals (ideally KMg3(Si3Al)O10(F,OH)2 - potassium-magnesium hydroxy-fluoro-aluminosilicate). Many of them display well-defined hexagonal crystal structures. I'm not exactly sure about the mineral content of the matrix - it possibly has titanate minerals (having TiO3) or armalcolite ((Mg,Fe,Al)(Ti,Fe)2O5). This rock comes from the Ellendale Center No. 5, a subcommercially diamondiferous lamproite body in the Ellendale Lamproite Field, northeastern margin of the Canning Basin, Kimberley, northern Western Australia. This Ellendale lamproite lava is Early Miocene in age (19-22 Ma). |
| Date | |
| Source | Phlogopite leucite lamproite lava (Ellendale Center No. 5, Lower Miocene, 19-22 Ma; Ellendale Lamproite Field, northeastern Canning Basin, northern Western Australia) 1 |
| 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@N05/15034287211 (archive). It was reviewed on 4 November 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 14:40, 4 November 2019 | | 3,008 × 2,000 (2.89 MB) | Ainz Ooal Gown (talk | contribs) | Transferred from Flickr via #flickr2commons |
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