VIRGINIA LOCALITIES 493 



cence and is easily decomposed b}^ HCl with the separation of gelatinous 

 silica. 



Weathered aUanite. — The weathered product of the fresh allanite (I) 

 analyzed by E. P. Valentine^^ (II of table below) was described by him 

 as compact earthy, breaking in angular pieces of brownish yellow, yellow- 

 ish red to red in color, but crumbling readily between the fingers and not 

 plastic. When heated in a closed tube, it yielded water which reacted 

 neutral, and blackened when heated on charcoal and l)ecame magnetic. 

 It was decomposed by HCl and was decomposed and partially dissolved 

 on boiling with NaOH. Particles of the crushed material were exam- 

 ined microscopically and found to be transparent, and of a wine-yellow 

 color, but without birefringence. 



Chemical analyses and their discussion. — The special features to which 

 attention is called in the analyses are (1) the large increase or gain in 

 water (hydration), which is considerably less than for the mineral from 

 either Amherst or Roanoke County; (2) the complete oxidation of fer- 

 rous to ferric oxide, and (3) the large total loss of the original mineral 

 removed in solution, amounting to 74.63 per cent. 



Analyses of fresh and decomposed Allanite from Nelson County, Virginia 



1'' II III IV V 



SiO, .30.04 18.66 9.12 ■ 90.88 27.30 



AI2O3 16.10 23.28 21.23 78.77 12.68 



Ce^Os 11.61 1.30 1.64 98.36 11.42 



DLO3 5.39 .65 1.77 98.23 5.29 



La^Oa 4.11 3.27 11.68 88.32 3.63 



Fe^Os 5.06 34.48 100.00 0.00 0.00 



FeO 9 . 89 none ) 



CaO 13.02 none} ^"^ ^^^'^ ^'^'^^ 



MgO 1.11 .29 3.84 96.16 1.07 



Na,0 28 .43 22.63 77.37 .22 



K2O 02 .20 100.00 0.00 0.00 



H2O 2.56 17.16 100.00 O.OO 0.00 



99.36 99.72 74.63 



Sp. gr 3.59 2.606 



T. Analysis of fresh allanite. C. G. Memminger, analyst. 

 II. Analysis of weathered allanite. E. P. Valentine, analyst. 

 III. Calculated percentage of each constituent saved. 

 IV. Calculated percentage of each constituent lost. 

 V. Calculated percentage loss for the entire mineral. 



81 E. P. Valentine : Am. Chem. Jour., vol. vii, 1885-1886, p. 178. 

 ®2 Includes SnO„ 0.17 per cent; MnO, trace. 



