Falcon's Eye

Finely fibrous, opaque aggregate formed when Quartz replaces the mineral crocidolite (type of asbestos), blue-grey to blue-green. Iridescence of planes. It is sensitive to some acids. Found associated with Tiger's eye. Used for ornamental objects and costume jewelry.
General Information
A variety or type of:Tiger's Eye, which is a variety of Quartz
Other Names/Trade Names:
Chemical Formula
SiO
 
2
Walter Schumann, Gemstones of the world (2001)
Physical Properties of Falcon's Eye
Mohs Hardness7
Walter Schumann, Gemstones of the world (2001)
More from other references
Specific Gravity2.58 to 2.64
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureIrregular
Walter Schumann, Gemstones of the world (2001)
Optical Properties of Falcon's Eye
Refractive Index1.534 to 1.540
Walter Schumann, Gemstones of the world (2001)
BirefringenceNone
Walter Schumann, Gemstones of the world (2001)
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
ChatoyancyChatoyant
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Blue-grey to blue-green
Walter Schumann, Gemstones of the world (2001)
More from other references
Causes of ColourThe blue colour is caused by Fe2+ compared to Fe3+ in the (oxidised) yellow/brown Tiger's Eye
Gemdat.org, Management Team (2012)
TransparencyOpaque
Walter Schumann, Gemstones of the world (2001)
LustreSilky
Walter Schumann, Gemstones of the world (2001) on fracturesMore from other references
Fluorescence & other light emissions
Fluorescence (General)None
Walter Schumann, Gemstones of the world (2001)
Crystallography of Falcon's Eye
Crystal SystemTrigonal
Walter Schumann, Gemstones of the world (2001)
More from other references
HabitFibrous aggregate
Walter Schumann, Gemstones of the world (2001)
Further Information
Mineral information:Falcon's Eye information at mindat.org
Copyright © Jolyon & Katya Ralph 1993-2014. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.