126 RE-EXAMINATION OP AMERICAN MINERALS. 



Mr. T. H. Garrett* has recently given an analysis of this 

 mineral. His results differ materially from those obtained 

 above. 



20. CUMMTNGTONITE — A HORNBLENDE. 



This mineral was described by Dewey,f and analyzed by 



Muir.J The latter obtained for its composition 



Si Fe Mn Na fi 



56.54 21.67 7.80 8.44 3.18=97.63 



Authentic specimens for examination were procured from 

 the Lederer collection in Yale College. Its structure is fibrous, 

 resembling anthophyllite ; luster silky; color ash-gray. It 

 occurs in mica slate at Cummington, Mass. Two analyses gave 



1 2 



Silica 51.09 50.74 



Alumina 95 .89 



Protoxide of iron 32.07 33.14 



Magnesia 10.29 10.31 



Manganese 1.50 1.77 



Lime trace trace 



Soda.... 75 .54 



Potash trace 



Water 3.04 3.04 



99.69 100.43 



These give the formula (FeMg) 4 Si 3 =R 3 Si 2 +ft Si. 



Atoms. At. weight. Per cent. Oxygen ratio. 



Silica 3 1731.93 53.59 3 



Protoxide iron 1\ 1125.00 34.80) ri 



Magnesia l| 375.00 11.61/ A * 



This is the chemical constitution of hornblende, and from 

 its physical characters it was long since referred to this species. 



21. Hydrous Anthophyllite— an Asbestus. 



Thomson gave this name to an asbestiform mineral, which 

 is found associated with chlorite on New York Island.g His 

 analysis gives 



Si Mg Fe Mn K £l H 



54.98 13.38 9.83 1.20 6.80 1.56 11.45=99.20 



We have received undoubted specimens of this mineral from 

 Messrs. Vaux, of Philadelphia, and Silas E. Horton, of JSTew 



* American Jour, of Science and Arts, May, 1853. 

 t Amer. Jour, of Science and Arts, 1st series, viii, 59. 

 t Thomson's Mineralogy, i, 493. 

 § Thomson's Mineralogy, i, 209. 



