VIII. A Study of Oil Shales and Torbanites

THE oil shales and torbanites form a group of materials which have in common the characteristic that on distillation they yield a product consisting typically of paraffins and olefines, and this feature is the source of their industrial importance.The Boghead coal or Torbanehill mineral of Armadale and Bathgate, Linlithgowshire, is the type of the torbanites or Boghead coals, and is the material originally distilled in Scotland for the manufacture of mineral oil.For oil-making this coal was exhausted in ten years, and for the past fifty years the Scottish industry has had to rely on the oil shales which occur in the Lothians, Fife, and Lanarkshire.Two varieties of torbanite occur in Linlithgowshire in the one seam-one brown, the other black.The former is the richer of the two, and of more restricted occurrence.It is very light in weight (sp.gr. about 1*2), tough, almost structure less megascopically, breaks with a conchoidal fracture, thin splinters being translucent and red in colour at the edges, has a light brown streak, and is most resistant to the weather.The black variety differs mainly in being of a dense black colour, with glossy fracture and brownish-black streak.The Lothians oil shales are heavy, laminated rocks (sp.gr.1-7 to 2*3), brown to black in colour, with pronounced bedding, which is particularly obvious after weathering or burning.Of the oil shales there are also two varieties-plain shale and " curly."The former is the more usual, and the latter seems to be produced from it by the effect of movements under pressure resulting in contortion of the bedding and the de velopment of numerous slickensides.