316 



REPORT OF NATIONAL MUSEUM, 1899. 



Co mjws it hn.— The varying composition of talc is shown in the series 

 of analyses o-iven below. 



Analyses of talc. 



The following analyses of soapstone have been made in the labora- 

 tory of the department: 



Analyses of soapstone. 



Locality. 



Francestown, New Hamp- 

 shire (Specimen No. 63166, 

 U.S.N.M.) 



Grafton, Vermont (Speci- 

 men No. 17569, U.S.N.M.). 



Dana, Massachusetts (Speci- 

 men No. 20439, U.S.N.M.) . . 



Baltimore County, Mary- 

 land (Specimen No. 26628, 

 U.S.N.M.) 



Guilford County, North Car- 

 olina (Specimen No. '''7662, 

 U.S.N.M.) 



Lafayette, Pennsylvania 

 (Specimen No. 63168, 

 U.S.N.M.) 



SiOo. AUOs. FeO. MgO. CaO. MnO. Na,,0. KoO. HjO. Totals. 



42. 43 

 51.20 

 38.37 



52. 70 



6.08 

 5.22 

 5.64 



5.57 



13.07 



8.45 

 8.86 



7.63 



7.38 



25.71 

 26. 79 

 28. 62 



26.88 



3.27 Trace 

 1.17 I 0.32 

 3.90 iTrace 



0.16 



1.77 



1.70 



33.72 1.34 



0.32 j 8.45 



99.49 



(■).yo 100.05 



14.49 99.88 



5.48 100.03 



I 

 10.78 I 99.93 



23. 00 99. 57 



Occurrence mid origin. — Talc in all its forms is presumably always 

 a secondary mineral, a product of alteration of other magnesian 

 silicates. 



Smyth has shown ^ that the talc beds of St. Lawrence County, New 

 York (Specimen No. 63173), are alteration products from schistose 

 aggregates of enstatite or tremolite, principally the former. Accord- 

 ing to this author, the talc occurs, not as has been stated, in the form 

 of a well-defined vein with walls of granite or gneiss, but in the beds 

 lying wholly within the schistose portions of the prevailing limestone. 



The following account of these deposits as occurring near Gouv- 

 erneur is by A. Sahlin:^ 



The A-illage of Gouverneur is situated near the northwest edge of a 

 geological island of Azoic rocks; granite, gneiss, limestone, and marble 



1 School of Mining and Forestry, XVII, No. 4, 1896. Also Fifteenth Annual 

 Eeport of the State Geologist of New York, 1895, pp. 665-671. 

 ^Mining and Scientific Press, May 11, 1893. 



