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| Chemistry:
(Ce,La,Nd,Th)PO4 [Cerium
Lanthanum Neodymium Thorium Phosphate] | Discovered
in 1829;
IMA
status: Valid (pre-IMA; Grandfathered). Monazite
is named from the Greek word monazein, meaning to
be solitary because of the rarity of the mineral
in the first known localities, plus "Ce" as
the cerium dominant member of the Monazite Series. |
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Classification
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Mineral
Classification: |
Phosphates |
Strunz 8th
Ed. ID:
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7/A.15-20 |
Nickel-Strunz 10th
Ed. ID:
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8.AD.50 |
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8 : PHOSPHATES, ARSENATES, VANADATES A : Phosphates, etc.
without additional anions, without H2O D : With only large cations
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Related
to: |
Monazite Group:
Monazite-(La), Monazite-(Ce), Monazite-(Nd), Monazite-(Sm),
Cheralite-(Ce), Brabantite
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Crystal
Data
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Crystallography:
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Monoclinic
- Prismatic
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Crystal
Habit:
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Crystals
typically tabular on [100], may be prismatic, equant
or wedge-shaped, to 27 cm; granular, massive.
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Twinning:
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Common,
[100] as twin and composition plane, as contact twins.
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Physical
Properties
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Cleavage: |
[100]
Distinct, [010] Poor; parting on [001] or [111]
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Fracture: |
Conchoidal
to Irregular/Uneven
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Tenacity:
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Brittle
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Hardness
(Mohs): |
5.0 - 5.5 |
Density:
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4.98 - 5.43 (g/cm3) |
Luminescence:
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Dull
brown cathodluminescence |
Radioactivity:
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If
rich in Thorium: Weak;
GRapi = 91,584.19
(Gamma Ray American Petroleum Institute Units) |
Other: |
Metamict
if rich in
Thorium. Paramagnetic
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Optical
Properties
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Color: |
Reddish
Brown, Brown, pale Yellow, Pink, Grayish White
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Transparency: |
Translucent
to Opaque |
Luster: |
Vitreous
to Sub-Adamantine, Resinous, Waxy |
Refractive
Index: |
1.770
- 1.860 Biaxial (+) |
Birefringence: |
0.053 - 0.067 |
Dispersion: |
r
< v or r > v, weak, horizontal |
Pleochroism: |
Weak;
Faint to imperceptible. In pale yellows. |
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Occurances
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Geological
Setting: |
An
accessory mineral in granites, syenites, and their pegmatites;
in carbonatites and volcanoclastic rocks; in fissure
veins and high-grade metamorphic rocks; commonly detrital
in river and beach sands; rarely authigenic in shales
and intense weathering zones. |
Common
Associations: |
Allanite,
Columbite, Thorite, Titanite, Wolframite, Xenotime,
Zircon (pegmatites and Alpine fissures); Cerianite,
Churchite, Florencite, Rhabdophane (Mt. Weld, Australia). |
Type
Locality: |
Ilmen Natural Reserve, Ilmen Mts, Chelyabinsk Oblast',
Southern Urals, Urals Region, Russia |
Year
Discovered: |
1829 |
View
mineral photos: |
Monazite
Mineral Photos and Locations |
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More
Information
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Mindat.org Webmineral.com |
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Monazite
is a very rare gem that is slightly radioactive as defined
in 49
CFR 173.403
(greater than 70 Bq/gram) due to the presence of Thorium (Th). Facetable
material is very rare as most Monazite is a dull and
opaque brown. Faceted gems are
usually very small but an intense reddish brown.
Monazite
is a primary ore of several rare earth elements (REE)
such as Thorium, Cerium and Lanthanum. Thorium is highly
radioactive. Since Monazite is radioactive it is often
metamict. Metamict is the condition when the radiation
destroys the crystal lattice completely while leaving
the outward appearance of the crystal unchanged. Increased
metamictation will increase the transformation of the
mineral's fracture from irregular/uneven to conchoidal.
Monazite
is widely distributed but gem quality crystals are quite
rare. The main sources of gems are Minas Gerais, Brazil
and Tsumeb, Namibia.
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Monazite
gems for sale:
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have not photographed our Monazite
gems. Please
check back soon.
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