250 Identity of Edwardsite loith Monazite. 



added that the prism was terminated by a four-sided pyramid. 

 He observed that the cleavage was sometimes perfect, but gene- 

 rally uneven parallel to the oblique terminal plane, but very per- 

 fect parallel to the longer diagonal. He further remarks that it 

 bore the closest resemblance to zircon, which the Monazite was 

 supposed to be by Menge, who first found it in the Ilmen branch 

 of the Uralian chain. The few measurements of Edwardsite 

 nearly correspond with those of Monazite, excepting the inclina- 

 tion of an oblique terminal plane to the plane replacing the ob- 

 tuse lateral edge, which, with Monazite, gave an angle of 100° 3'', 

 with Edwardsite 103° 58', but the calculation of the former was 

 grounded on imperfect measurements. In regard to form, there- 

 fore, the two minerals correspond. 



" They also resemble each other in relation to other properties. 

 Color, hyacinth red to reddish brown, the lustre of Edwardsite 

 somewhat stronger ; hardness = 5 (apatite). Specific gravity of 

 Edwardsite is rated too low by Shepard = 4.2 to 4.6, — that of 

 Monazite, according to Breithaupt ~- 4.992 to 5.079. In behav- 

 ior before the blowpipe alone, or with fluxes, both alike, both in- 

 fusible. Shepard observes that the former fuses with great diffi- 

 culty on the edges, but no such fusion was observable on the 

 specimen in the royal cabinet. There are some differences in 

 their behavior with acids, the former, according to Shepard, being 

 slightly aff'ected by aqua regia, the Monazite, according to Ker- 

 sten being decomposed by chlorohydric acid with the evolution 

 of chlorine. 



" The apparent diff'erences of their chemical composition may 

 be reconciled. The Monazite was analyzed by Kersten, the 

 Edwardsite by Shepard. 



* There is evidently sgine error in the figures of this analysis, for the sum of those given is 101.49. 



