S. Weidman — Amphibole Hudsonite. 





I 



II 



III 



IV 



V 



VI 



VII 



VIII 



SiO„ . 



.-43-85 



42-00 



36-86 



42-46 



38-41 



35-42 



3418 



36-78 



Tio; . 







1-04 







1-34 



1-53 





A1.,0 3 



.. 4-45 



12-00 



12-10 



11-45 



17*65 



8-89 



11-52 



15-13 



*v>, 



.. 3-80 





7-41 



6-18 



3-75 



9-73 



12-62 



14-46 



FeO _ 



..33-43 



30-00 



23-35 



19-93 



21-75 



24-48 



21-98 



22-89 



MnO. 



. . 0'45 



0-25 



•77 



•75 



0'15 



1-17 



0-63 





CaO . 



. . 4-65 



11-00 



10-59 



10-24 



10-52 



6-93 



9-87 



5-14 



MgO 



.. 0-81 



2-25 



1-90 



1-11 



2-54 



0-17 



1-35 



0-93 



Na„0 



.. 8*15 





3-20 



6-08 



2-95 



5-13 



3-29 



4-00 



K 3 _ 



.. 1-C6 



trace 



1-20 



1-44 



1-95 



3-23 



2-29 



042 



H 2 0. 



.. 0-15 



0-75 



1-30 





•24 



3-15 



•35 



•25 



]00'80 98-25 99-61 99'64 99*91 99'64 99*61 lOO'OO 



I — Arfvedsonite, Kangerdluarsuk, Greenland. Lorenzen, Min. Mag., v, 

 50, 1882. II — Noralite, Nora, Westmanland, Sweden. Klaproth, Beitrage, 

 v, 153, 1810. Ill— Hudsonite, Cornwall, N. Y. Analysis by J. L. Nelson 

 and W. W. Daniells. IV — Barkevikite, Barkevik, Norway. Analysis by G. 

 Flink, Brogger, Zeit. d. Kryst., xvi, 142, 1890. V— Barkevikite, Square 

 Butte, Mont. Lindgren and Melville, this Journal, xlv, 292, 1890. VI— Am- 

 phibole, Beverly, Mass". F. E. Wright, Tscherniak's Min. u. Petrog. Mitth., 

 xix, 312, 1900. VII — Hastingsite, Dungannon, Ontario. Adams and Har- 

 rington, this Journal, ii, 213, 1896. VIII — Bergamaskite, Monte Altino, 

 Bergamo, Italy. Lucchetti, Groth's Zeitschr., vi, 199. 



These amphiboles are seen to have a low content of silica, and 

 if the content of Ti0 2 had been determined in each case, it is 

 likely the similarity in amount of Si0 2 as well as Ti0 2 would 

 be still more apparent. Next in amount to silica is the iron, 

 which prevails in the protoxide form ; the alumina is abundant 

 though variable ; the lime is greatly in excess of magnesia ; 

 and the alkalies, especially soda, occur in considerable quantity. 

 The amphibole noralite was analyzed by Klaproth in 1810 

 and the analysis should be taken with some reservation, for good 

 methods for determining the mineral constituents, and especially 

 the alkalies, had not at that time been devised. The noralite, 

 however, seems well worthy our attention in comparison with the 

 other amphiboles of this table. The hudsonite appears to be 

 more nearly like VII, hastingsite, in composition than the 

 others. Their optical properties, especially the inclination of 

 the plane of extinction to the vertical axis, appear to be quite 

 variable. So far as recorded, the angles of extinction are as 

 follows: arfvedsonite, c A c(3)= —14°; hudsonite, c /\ 6 = 

 -f 9°; barkevikite, Barkevik, c /\ 6 = -f 12^°; barkevikite, Square 

 Butte, c /\ c = + 13°; amphibole, Beverly, c /n e=4- 21. 

 So far as principal features of composition are concerned, 

 all these amphiboles might well be placed in the same 

 class with arfvedsonite, though retaining in each case their 

 varietal names on account of slight differences in composition 

 and in optical properties. 



Geological and Natural History Survey of Wisconsin, 

 Madison, Wisconsin. 



