Fire opal

Description

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.)

Risks

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

• Mineral Galleries at http://mineral.galleries.com/minerals/mineralo/opal/opal.htm Mohs hardness=5.5-6.0

• Wikipedia: http://en.wikipedia.org/wiki/Opal (accessed Oct. 12, 2005) specific gravity=2.1=2.3; RI=1.44 -1.46; Mohs hardness=5.5-6.6

• 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