Torbanite, also known historically as boghead coal or kerosene shale, is a variety of fine-grained black oil shale. It usually occurs as lenticular masses, often associated with deposits of Permian coals.[1][2] Torbanite is classified as lacustrine type oil shale.[3] A similar mineral, cannel coal, is classified as being a terrestrial form of oil shale, not a lacustrine type.[3]
Torbanite is named after Torbane Hill near Bathgate in West Lothian, Scotland, a major location of occurrence.[4] Torbanite found in Bathgate may have formations of bathvillite found within it.[5] Historically, two other names have been used for torbanite. Boghead coal is named after Boghead estate, also near Bathgate in Scotland. In Australia, the historical name for torbanite was kerosene shale.[6][7]
Other major deposits of torbanite are found in Pennsylvania and Illinois, US, in Mpumalanga Province in South Africa, in the Sydney Basin of New South Wales, Australia,[8] the largest deposit of which is located at Glen Davis, and in Nova Scotia, Canada.[1][4]
Organic matter (telalginite) in torbanite is derived from lipid-rich microscopic plant remains similar in appearance to the fresh-water colonial green alga Botryococcus braunii.[1][2][4] This evidence and extracellular hydrocarbons produced by the alga have led scientists to examine the alga as a source of Permian torbanites[9] and a possible producer of biofuels.[10][11] Torbanite consists of subordinate amounts of vitrinite and inertinite; however, their occurrence varies depending on deposits.[4]
A rubber-like, elastic, highly-resilient bituminous substance, known as coorongite—classified as an organic-rich sediment and named after the Coorong where it was found—has been identified as a 'peat stage' in the formation of torbanite. It provides evidence of the lacustrine and algal origin of torbanite.[6][12][13][14][11] Substances very similar to coorongite had other historical names, depending upon the location of the deposits, such as n'hangellite from Portuguese East African (now Mozambique) and marahunite from Brazil.[15]
Torbanite typically comprises 88% carbon and 11% hydrogen.[1] Paraffin oil can be distilled from some forms of torbanite, a process discovered and patented by James Young in 1851.
See also
References
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