210 



BOCK BISINTSaBATION AND DECOMPOSITION 



feet below the surface and showed under the microscope a pre- 

 ponderance of bleached and iron-stained mica in scales so soft 

 and inelastic as to resemble talc. A few granules thought to be 

 pyroxene were still intact, while there remained an abundant 

 sprinkling of magnetite and perofskite. The serpentine of the 

 original rock had totally disappeared. The results of the an- 

 alyses and calculations are given below, the titanic oxide and 

 alumina, taken together, having been assumed as a basis for 

 comparison : 



Analyses of Feesh and Decomposed Alnoite, Hebkimer County, 



New York 





I 



II 



III 



IV 



Y 



VI 



VII 



CONSTITITENTO 



D 



w 



ft 



W 







WB 

 H 



f*i XLx M 



05 a 



9 H t^ 

 « ^ !« 





SiOj. . . . 

 TiO^ . . . 



A1203 . . . 



PeA • • • 



FeO ... 



MgO . . . 

 CaO. . . . 

 KgO. . . . 

 Na20 . . . 

 Ignition . . 



fo 



35.25 

 2.25 

 6.10 

 8.53 

 6.60 



20.40 

 7.40 

 2.88 

 0.70 



10.15 



% 



33.10 

 2.90 

 7.88 



16.71 

 1.48 



13.42 

 5.25 

 0.29 

 0.23 



17.85 



% 

 35 51 



2.27 

 6.14 

 8.59 

 5.64 



20.55 

 7.46 

 2.90 

 0.71 



10.23 



% 



33.40 

 2.93 \ 

 7.95 J 



16.86 \ 

 1.49/ 



13.54 

 5.30 

 0.29 

 0.23 



18.01 



9.69 

 0.00 



0.55 



10.08 

 3.36 

 2.68 

 0.53 

 0.00 



% 



72.69 

 100.00 



96 30 



51.03 



54.90 



7.73 



25.03 



100.00 



% 



27.31 

 0.00 



3.70 



48.97 

 45.10 

 92.27 

 74.97 

 00 



Total . . 



99.26 



99.11 



100.00 



100.00 



26.89 







The loss of 27.31% of the original silica in a rock so low in 

 alkalies is worthy of note, as is also the fact that the decompo- 

 sition, seemingly so thorough, was accompanied by a loss of but 

 26.89% of materials of all kinds. That 93.45% of the fresh rock 

 and 93.60% of the decomposed was soluble in dilute hydrochloric 

 acid and sodium carbonate solutions is of interest in connection 

 with what is stated on page 201. The maximum range of tem- 

 perature of the region is from about — 6*^ to -^- 95^ Fahr., with 

 an annual precipitation of 43 inches. 



