Monazite

Big Photo

Brazil
0.16 carats
© Brian Kosnar - Mineral Classics

Monazite is named after Greek "monazein" - to be solitary, alluding to its rare occurence as isolated crystals in the mineral's discovery material. The three minerals are monazite-(Ce), monazite-(La) and monazite-(Nd).

Monazite forms tabular or prismatic crystals of yellow, yellow-brown, brown, rose-red, reddish-brown colour. Colour change from reddish orange in daylight to pinkish brown in tungsten light has been reported.

Monazite usually contains small amounts of Th or sometimes U, both making it radioactive.
General Information
Chemical Formula
(Ce,La,Nd,Th)PO
 
4
Michael O’Donoghue, Gems, Sixth Edition (2006)
Photos of natural/un-cut material from mindat.org
Physical Properties of Monazite
Mohs Hardness5 to 5.5
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Specific Gravity4.80 to 5.50
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical Properties of Monazite
Refractive Index1.796 to 1.841
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Optical CharacterBiaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Birefringence0.045
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Colour
Colour (General)Yellow, yellow-brown, brown
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Colour change: reddish-orange/greenishMore from other references
Colour (Daylight)Colour change (reddish orange in daylight to pinkish brown in tungsten light) is reported but is common enough when RE are involved in the composition.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Colour (Incandescent Light)Colour change (reddish orange in daylight to pinkish brown in tungsten light) is reported but is common enough when RE are involved in the composition.
Michael O’Donoghue, Gems, Sixth Edition (2006)
TransparencyTransparent
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Fluorescence & other light emissions
Fluorescence (Long-Wave UV)Some specimens have shown a greenish fluorescence
Michael O’Donoghue, Gems, Sixth Edition (2006)
Crystallography of Monazite
Crystal SystemMonoclinic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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HabitTabular, prismatic
Michael O’Donoghue, Gems, Sixth Edition (2006)
Geological Environment
Where found:Is found in igneous rocks including granite pegmatites
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Monazite information at mindat.org
Significant Gem Localities
Madagascar
 
  • Analamanga
    • Ankazobe District
      • Ambolotarakely
Madagascar, extraLapis, English No.1, 2001, p. 44
Madagascar, extraLapis, English No.1, 2001, p. 44
Sri Lanka
 
  • Sabaragamuwa Province
    • Ratnapura District
      • Ratnapura
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 431
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