Monazite - (Ce,La,Th)PO4

Monazite is a REE phosphate of variable composition, in the monazite Ce(La,Th) ions are surrounded by nine oxygens of the tetrahedral phosphate groups. In monazite may be present all REE elements, but Ce is most common.

Substitution may occur for Th4+ + Ca2+ → 2Ce3+ and for (SiO4)4- or (SO4)2- groups usually replace tetrahedra PO4 3-

Optical Properties:

• Relief: High
• Color: strong interference colors from upper third to fourth orders
• Interference distinct on (100), poor on (010) intersecting at 90°
• Form: blocky euhedral crystals

Monazite is a accessory minerals in granite, granodiorite, syenite and other similar plutonic rocks, in pegmatite occur in large euhedral crystals.

Bibliography



• Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen


Photo
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. XPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. XPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. XPL image. 10x (Field of view = 2mm)
monazite087.jpg

Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. XPL image. 10x (Field of view = 2mm)
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Monazite crystal. XPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)
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Monazite crystal. PPL image. 10x (Field of view = 2mm)