CIIAPTKK XI 



COLUMBATES, PHOSPHATES, VANADATES, INCLUDING 

 NITRATES, BORATES, AND URANATES 



MONAZITE 



Monazite. (Ce.La.Di)PO 4 ; an orthophosphate of the rare 

 earths, cerium, lamthanum, and didymium ; Monoclinic ; Type, 

 Digonal Equatorial ; Ce 2 ,O 3 = 37.26, (Ce . La . Di) 2 O 3 = 31.60, P 2 O6 

 = 29.32, ThO 2 = 1.48; SiO 2 = .32 (North Carolina) ; ft: b: c = 

 9693 ; 1 : .9256 ; p = 76 20' = 001 A 100 ; 001 A 110 = 43 17' ; 

 001 A 101 = 37 7' ; 001 A 011=41 58'; 101 A 100 = 39 12' ; 

 111 A 100 =_ 48 30'; Common forms, a (100), b (010), m (110), 

 w(101), x(101), r(lll), v(lll), e(011); Twinning plane, 100; 

 Cleavage, basal perfect, a distinct, b difficult ; Brittle ; Fracture, 

 uneven ; H. = 5-5.5 ; G. = 4.9-5.3 ; Color, clove-brown to yellow- 

 brown, and red; Streak, white to yellowish; Luster, somewhat 

 resinous; Translucent to opaque ; a =1.796; p =.1796; \ = 1.841; 

 y a = .045; Optically (+); Axial plane perpendicular to 010; 

 Bx aA c = 2 6' 30" in front; 2E = 24 36'. 



B.B. Infusible ; powdered and fused with soda, then dis- 

 solved in HNO 3 , yields a yellow precipitate with ammonium 

 molybdate, or the powered mineral moistened with H 2 SO 4 yields 

 a green flame. In O. F. reacts for the rare earths. Page 572, de- 

 composed with H 2 SO 4 , but difficultly soluble in HC1. 



General description. Crystals are tabular parallel to the 

 orthopinacoid or elongated parallel to the orthoaxis, also massive 

 or in rounded disseminated grains. 



Monazite is an accessory mineral in certain granites, granitic 

 gneisses, and pegmatites. Chemically it always contains some 

 thorium, which may amount in some cases to 9 per cent, of ThO 2 . 

 In such cases it becomes a source of this rare earth, which is now 

 used in considerable quantities in the manufacture of incandescent 

 gas mantles. The bulk of the commercial supply of monazite is 

 derived from Brazil, where it is separated from detrital sands. In 

 the United States the supply is concentrated from sands at several 



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