Monazite-(Ce)
Image: Robert M. Lavinsky (CC BY-SA 3.0)
Mineral NameMonazite-(Ce)
Chemical Formula(Ce,La,Nd,Th)PO₄
Mohs Hardness5
Crystal Systemmonoclinic
Lusterresinous
Streak Colorwhite
Cleavagedistinct on {100}, poor on {010}
Fractureconchoidal
Specific Gravity4.6
Colorsreddish-orange, yellowish-brown, brown, green
Transparencytranslucent
Type LocalitySiglo Veinte Mine (Siglo XX Mine; Llallagua Mine; Catavi), Llallagua, Rafael Bustillo Province, Potosí Department, Bolivia
Mineral GroupPhosphates
Usesore of rare-earth elements, ore of thorium, catalysts, minor gemstone
Associated Mineralsquartz, feldspar, zircon, ilmenite, rutile
Rarityuncommon
Description
This specimen features a prominent reddish-orange, star-shaped aggregate of twinned Monazite-(Ce) crystals, contrasting against a matrix of lighter, possibly yellowish, crystalline material.
Geological Context
Monazite-(Ce) is a primary accessory mineral found in granites, pegmatites, gneisses, and other metamorphic rocks, often forming in high-temperature environments. It is also concentrated in placer deposits due to its high specific gravity and resistance to weathering.
