Tungstates and Phosphates: Monazite
(including Arsenates and Vanadates)

Composition: (Ce,La,Y,Th)PO₄

Crystal system: Monoclinic; crystals usually equant, also as discrete grains in sands

8.4.1
cleavable monazite
Mica Creek north west Qld Australia

Properties:

• Resinous lustre
• Yellowish to reddish brown color
• White to light brown streak
• Knife barely scratches (Mohs Hardness 5-5.5)
• High to very high density
• Cleavage rarely obvious
• Query uneven fracture
• Not ferromagnetic
• Reacts very slowly with hydrochloric acid (HCl)

Occurrence:

Monazite occurs as an accessory mineral in igneous rocks and in heavy mineral sand deposits with minerals such as rutile, ilmenite, zircon and cassiterite.

8.4.2
cleavable monazite
Mica Creek north west Qld Australia

Monazite is an important source of rare earths that are used as catalysts in processes such as petroleum refining.