42 JOURNAL OF THE 



The optical properties of mouazite are: — thin sec- 

 tions, b}^ transmitted ligfht, arc colorless to yellowish; 

 pleochroism is g"enerally scarcely noticeable; absorption 

 b is g-reater than c = a; the plane of the optic axis is 

 perpendicular to the plane of of S3'nimetry, that is the 

 clino-pinacoid, the positive a.cute bisectrix lies iu the 

 oblique ang-le /?, hence sections parallel to the basal 

 pinacoid show the full interference figure; the extinc- 

 tion angle varies from l'^04^ to 5" 54^ ; the optical angle 

 is small, 2E (red) = 25»22\ 2E (yellow) ^ 24°56\ 2V 

 (yellow) = 12°44S (from Schiittenhofen, Bohemia); the 

 dispersion is weak and horizontal; the single refrac- 

 tion is high, and the double refraction considerable, y 

 — a= 0.0454, y — ^ 0.0446, fi — a =0.0008 (from Aren- 

 dal, Norway). 



DISTRIBUTION AND MODES OF OCCURRENCE- 



Until comparatively recently the localities in which 

 monazite was found were few and far between. The 

 original specimen of turnerite came from the Dau- 

 phine in France; in 1826 Menge discovered some crys- 

 tals in the Ilmen Mountains of Russia; it was then 

 found in the United States at Norwich and Watertown, 

 Conn. Up to the present time, it has been found in 

 over 75 localities in the United States, Canada, South 

 America, England, Sweden, Norway, Finnish Lap- 

 mark, Russia, Belgium, France, Switzerland, Ger- 

 many, Austria and Australia. And the probabilities 

 are that these localities will be rapidly added to in the 

 future. 



Monazite is an accessory constituent of the granite 

 eruptives and their derived gneisses. It has been found 

 in these rocks over widely separated areas of the 

 Earth's surface, and further search and study is liable 

 to reveal its more general presence in similar rocks, 



