104 THE OCCURRENCE OF ALLANITE 



Journ. Science [2] xix., 20.) The specific gravity, however, is con- 

 siderably lower than in these latter varieties, and in others from Penn- 

 sylvania analysed by Genth. One specimen gave me 3.255 ; another, 

 apparently quite free from foreign matter, and carefully weighed,. 

 3.288. Rammelsberg's specimen from East Bradford, Pa., gave 3.535 ; 

 and that from Orange County, New York, as examined by Genth, 

 yielded 3.782. Prof. Brush (Dana's Mineralogy, first supplement) 

 obtained from the latter a still higher value, 3.935. The Pennsylvania 

 specimens analysed by Genth varied in sp. gr. from 3.491 to 3.831. 

 The lowest recorded density of allanite is 3. 193, found by A. Erdmann 

 in a blackish-green variety from Tunaberg, Sweden. These variations, 

 although, perhaps, partly due to structural differences, arise most 

 probably from the variable amount of water present in the different 

 specimens. 



The leading characters of the Muskoka allanite are as follows : — 



Amorp^ious : with compact structure ; shining, pitch-like lustre y 

 and more or less conchoidal fracture. Colour, jet-black ; streak, 

 light-grey. H = 5.75 ; sp. gr. = 3.288. 



Heated in the bulb-tube, it decrepitates, and gives off a small 

 quantity of water. 



Before the blow-pipe, it intumesces exceedingly, and fuses with great 

 readiness into a black, opaque, and very feebly magnetic globule. 



"With Borax, it is rapidly attacked, and is dissolved in considerable 

 quantity. The glass shews the reactions of cerium and iron oxides. 

 If a little phosphor-salt be added to it, the glass may be rendered 

 milky by flaming. This reaction, not hitherto noticed in books, holds 

 good with other silicates of cerium. 



With phosphor-salt, a " silica skeleton " is obtained, and the glass 

 becomes opaline on cooling. 



With carb. soda, the test-substance forms a yellowish slaggy mass, 

 which, on the addition of a little nitre, exhibits the reaction of man- 

 ganese. 



In boiling chlorhydric acid, decomposition is readily effected — the 

 silica separating in a gelatinous state. 



The filtered liquid yields a precipitate with ammonia, from which, 

 a certain amount of alumina is dissolved out by caustic potash. In 

 the original solution, filtered from the ammonia precipitate, oxalic acid 

 shews the presence of lime. 



