Monazite

Formula:  (Ce,La,Nd,Th)PO4

Origin of name:  From Greek for to be solitary

 

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:  Common on {100}, sometimes cruciform; rare on {001}, lamellar

Unit cell: a = 6.84 Å, b = 7.07 Å, c = 6.45 Å, β = 103.9°

 

Colour:  Reddish-brown, pink, yellow-brown, green, gray-white

Diaphaneity: 

Luster:  Resinous, waxy

Habit:  Crystals thin to thick tabular, small, elongated along c-axis; also equant, wedge-shaped or prismatic; massive granular

Hardness:  5 to 5.5

Specific gravity:  4.6 to 5.4

Cleavage:  5; {100} distinct, {010} less distinct, {110}, {101} and {011} indistinct

Tenacity:  Brittle

Streak: 

 

Synonyms/varieties:  kularite

 

Comments:  Three distinct species with the extensions -(Ce), -(La) and -(Nd) indicating the predominant rare earth cation in the formula

 

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