Sentence Examples

  • A structure akin to cleavage, often exemplified by slates especially when they have been somewhat contorted or gnarled, is the Ausweichungsclivage of Albert Heim.
  • The faces of slates have usually a slightly silky lustre due to the abundance of minute scales of mica all lying parallel and reflecting light simultaneously from their pearly basal planes.
  • In microscopic section the best slates show much colourless mica in small, thin, irregular scales.
  • Minute rods or needles of rutile are also common in slates, and well-formed cubes of pyrites are often visible on the splitting faces.
  • The brownish colour of some slates is due to limonite and haematite, but magnetite occurs in the darker coloured varieties.

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