ANALYSES OF DIABASE FROM MEDFORD. 



353 



from the ferruginous silicates, there are no other observable signs of de- 

 composition, though the presence of a soda-bearing zeolite is indicated 

 by cubes of chloride of sodium, which separate out when an uncovered 

 slide is treated with a drop of hydrochloric acid. 



Analyses of fresh and disintegrated Diabase from Medford. 





Fresh diabase. 



Disintegrated 



Silt from disintegrated 

 diabase, numbers 7, 8 











;£iac. 



and 9 of table, on p. 352. 





1 



2 



3 



4 



5 



6 



7 







^•So^ 





^•Bi 



G 



GO 









^0)^. 





^oR. 



t» c^ 



rw 





Constituents. 



m 



1 



Analysis of 

 tion solubl 

 HClandNa 





Analysis of 

 tion solubl 

 HClandNa 



<^ G^ 

 t-- 



J- (1) oS 







o.^ rinHCl \ 

 ^'^nin Na,C03r- 



47.28 



/ 1.19 

 \ 9.66 



1 44.44 



/ 0.85 

 I 8.65 



0.47 

 22.63 



1 13.51 



36.61 



AlA 



20.22 



4.74 



23.19 



4.86 



21.98 



) 





Fe,Oo 



3.66 

 8.89 

 7.09 

 3.17 



1 10.91 



3.09 



2.20 



12.70 



6.03 



2.82- 



10.00 



1.50 

 1.84 



12.83 



3.32 

 3.23 



y 5.88 



0.12 

 0.79 



40 68 



FeO 





GaO 



3.44 



M<?0 



4.02 



MnO 



0.77 



Not det. 



0.52 



Not det. 



Not det. 



Not ^et. 



Not det. 



K2O 



2.16 



1.21 



1.75 



0.68 



1.30 



0.52 



1.82 



Na20 



3.94 

 0.68 

 2.73 



0.50 

 Not det. 

 2.73 



3.93 

 0.70 

 3.73 



0.17 

 Not det. 

 3.73 



0.90 



^^>4 



2.14 



P,,0, 



Not det. Notdpt 





Ign 



10.86 



0.11 



10.97 









100.59 



36.23 



99.81 



32.28 



77.52 



22.17 



99.68 



A glance at this table is sufficient to show that the disintegration is 

 accompanied by decomposition and a leaching action which has resulted 

 in the removal of a portion of the more soluble constituents. The fact 

 that the fresh rock yields the larger percentages of its constituents to the 

 solvent action of acid and alkaline solutions is readily explained on this 

 ground, though I doubt if the full significance of the fact, so far as it 

 relates to silicious crystallines, is as yet appreciated. It will be observed 

 that 36.28 percent of the fresh rock and 32.28 per cent of the decomposed 

 is thus extracted. 



Of the material classed as silt in columns 5, 6 and 7, or as silt and clay, 

 by Professor Whitney, on page 352, and which constitutes only some 3.17 

 per cent of the entire residual debris, 77.87 per cent is soluble in dilute 



