Jaffeite: Properties and Occurrences

Jaffeite is a hydrated calcium silicate with the following chemical formula: Ca6Si2O7(OH)6. It is a hydrated calcium silicate mineral. The mineral was first found at the Kombat Mine in Namibia. In 1989 the mineral was named after Prof. Howard W. Jaffe (1919–2002) of the University of Massachusetts Amherst.

General information

  • Formula: Ca6Si2O7(OH)6.
  • Specific Gravity: 2.65
  • Crystal System: Trigonal
  • Transparency: Transparent

Fig: Jaffeite – a hydrated calcium silicate


Jatreite is transparent and colorless with a vitreous luster and a white streak. It is brittle and the fracture is conchoidal. It forms euhedral and subhedral crystals closely associated with and commonly contained within idio. morphic laths of defernite approximately I cm in diameter.

  • Cleavage:{???} Indistinct
  • Color:
  • Density: 2.65
  • Diaphaneity: Transparent
  • Luster: Vitreous (Glassy)
  • Streak: white
  • Tenacity: Brittle

Occurrence: Closely associated with or enclosed by defernite within low-grade metamorphic rocks.

Association: Defernite, hausmannite, apatite, brucite, hillebrandite, vesuvianite, glaucochroite, galena, copper.


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