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Formula | (Cl,La,Th)PO4 | |
Crystal System | monoclinic | |
Crystal Habit | small equant or elongate crystals | simple twins on {001} are common |
Cleavage | {100} is distinct |
conchoidal fracture, brittle |
Color/Pleochroism | Olive or yellowish-green in hand samples. Colorless to pale green in thin section. Weak, pale green pleochroism in thin section. | |
Optic Sign | Biaxial (+) | |
2V | 7-19 | |
Optic Orientation | X=b
O.A.P. = (010) |
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Refractive Indices
alpha = beta = gamma = delta = |
1.774-1.800 1.777-1.801 1.828-1.851 0.045-0.075 |
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Max Birefringence | 0.045-0.075 | |
Extinction | parallel | |
Distinguishing Features | In thin section: high birefringence, high relief, and pale yellow color. Staurolite is more distinctly pleochroic and has much lower birefringence. Some grains may resemble zircon, titanite, xenotime, or members of the epidote family. | |
Occurrence | Monazite is an accesory mineral in granite, granitic pegmatite, syenite, and carbonatites. Because it is stable in the weathering environment, monazite may be part of the heavy mineral fraction of the clastic sediments. It is infrequently found in hydrothermal vein deposits. In metamorphic rocks it is found in metamorphosed dolostone and in mica schist, gneiss, and granulites. (Nesse, W.D. 2000. Introduction to Mineralogy. New York, NY: Oxford University Press, Inc. pp. 349-50.) | |
Editors | Merilie Reynolds '08 |