Monazite
A variety of Monazite Group
What is Monazite?
Monazite – which often occurs in very fine grains and usually takes on a yellow- or reddish-brown hue – can be broken down into five subtypes, each of which is defined by a precise chemical composition. The mineral is commonly mined, both because it contains rare-earth metals such as thorium, and because it commonly associates with precious metals and gemstones, including gold, platinum, garnets, and zircon.
Etymology & Origins
The name monazite comes from the Greek μονάζειν (to be solitary), via German Monazit, in allusion to its isolated crystals.
Uses & Applications
Monazite is often mined as an ore for several rare elements and minerals. Thorium is one important component of this rock that can be used to generate nuclear power because it is very radioactive. Because monazite has these radioactive properties, it is often used for radioactive dating as well. It is also an important source of cerium and lanthanum.
Optical Properties
- Refractive Index
- 1.796-1.841
- Birefringence
- 0.045
- Optical Character
- Biaxial positive
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Key Characteristics
Composition of Monazite
All monazites adopt the same structure, meaning that the connectivity of the atoms is very similar to other compounds of the type M(III)PO4. The M(III) centers have a distorted coordination sphere being surrounded by eight oxides with M–O distances around 2.6 Å in length. The phosphate anion is tetrahedral, as usual. The same structural motif is observed for lead chromate (PbCrO4).
Health & Safety Information
- ⚠️Harm Reason: Monazite is toxic due to its Radioactivity.
- ⚠️Radioactivity: Monazite contains rare earth elements which are often related to radioactive thorium and uranium. It is good to use a Geiger counter to assess the hazards prior to handling.
- ⚠️How to prevent the risks of Monazite?
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Quick Facts
Physical Properties
- Color
- Commonly reddish brown, yellowish brown, greenish brown, rarely nearly white; yellow, colorless in transmitted light
- Hardness (Mohs)
- 5 - 5.5
- Density
- 4.6 - 5.7 g/cm³
- Streak
- White
- Luster
- Vitreous, Resinous, Waxy
- Crystal System
- Monoclinic
Chemical Properties
- Chemical Formula
- (REE/Ce/La/Nd/Sm/Gd)(PO4)
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