Fire opal

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A brilliant red and orange Opal. Fire opals have been mined in Mexico for over 500 years. Current mines in Mexico are at Queretaro and Magdalena.

Synonyms and Related Terms

girasol; Mexican opal; water opal; jelly opal; opala de fogo (Port.); Feueropal (Deut.)


Highly hydrated; may be subject to dehydration and surface cracking.

Physical and Chemical Properties

  • Mineral system=amorphous
  • Cleavage=none
  • Fracture=conchoidal
  • Luster=vitreous to resinous
  • Streak=white
  • Fluoresce=usually white or pale green, some samples phosphoresce
Composition SiO2·nH2O
Mohs Hardness 5.5-6.0
Density 2.1-2.3 g/ml
Refractive Index 1.44-1.46

Resources and Citations

  • Yasukazu Suwa, Gemstones: Quality and Value, Volume 1, Sekai Bunka Publishing Inc., Tokyo, 1999 Comment: RI=1.450; Specific gravity=2.15
  • Michael O'Donoghue and Louise Joyner, Identification of Gemstones, Butterworth-Heinemann, Oxford, 2003 Comment: RI=1.45; Specific gravity=2.10
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

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