Tainiolite, which is named from the Greek for band or strip, is certainly not a well know mineral. An alternate and widely used spelling for tainiolite was taeniolite, but now tainiolite is the official spelling. Tainiolite is a rare mica mineral. It is a true mica closely related to other lithium rich micas; lepidolite and polylithionite. Tainiolite, like other micas, has a layered structure of lithium aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage. Tainiolite is easily confused with polylithionite but is comepletely non-fluorescent unlike polylithionite.


  • Color is colorless, tan, brown to silvery.
  • Luster is vitreous to pearly.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include thin lamellar tabular to platy crystals forming "books", scales and tapering prisms.
  • Cleavage is perfect in one direction producing thin sheets or flakes.
  • Fracture is not readily observed due to cleavage but is uneven.
  • Hardness is 2.5 - 3.
  • Specific Gravity is approximately 2.8 - 2.9 (average)
  • Streak is white.
  • Other Characteristics: Non-fluorecent as opposed to polythionite.
  • Associated Minerals are natrolite, fluorite, microcline, pectolite, quartz,phillipsite, richterite and aegirine, among other rare minerals.
  • Noteable Occurrences include the type locality of Narsarsuk, Greenland as well as Lovozero Massif, Kola Peninsula, Russia; Magnet Cove, Arkansas and Coyote Peak, Humboldt County, California, USA and Mont Saint-Hilaire, Quebec, Canada.
  • Best Field Indicators are crystal habit, non-fluorescence, color, cleavage, locality and associations.

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