204 



bock: disintegeation and decomposition" 



Nos. 2, 3, and 4 show clearly to the unaided eye the com- 

 pound character of the mass, and when examined under the 

 microscope, distinct particles of the undecomposed silicate min- 

 erals with an abundance of magnetite are to be seen. In No. 5 

 the decayed products become more differentiated into kaolin and 

 iron oxide, with the usual amount of magnetite and some of the 

 undecomposed silicate minerals still discernible. Nos. 6 and 7 

 represent highly colored ferruginous masses in which a slight 

 sprinkling of the feldspar, augite and magnetite can still be 

 recognized, though to a very much less degree in No. 7 than in 

 No. 6. No. 8 is a deep buff-colored mass of fine clay showing no 

 trace of the original minerals whatsoever. 



According to the analyses and calculations given below, 

 there has been a total loss amounting to 70.31% or more than 

 two-thirds of the original material. This includes a loss of 

 73.64% of the original silica, 68.19% of the alumina, 98.68% 

 of the lime, 98.81% of the magnesia, 82.46% of the soda, and 

 77.31% of the potash. 44.59% of the fresh rock was soluble 

 in dilute hydrochloric acid and sodium carbonate solutions, and 



Analyses of Press and Decomposed Olivine Diabase, from Chatham, 



Virginia 





Fresh 



Decomposed 



Calculated 



Calculated Amounts 





Diabase 



Diabase 



TO Total 

 OF 100 



Saved and Lost 



ElI 



I 



II 



III 



IV 



V 



VI 



VII 



VIII 



IX 



g 





i^ 





i:^ 









on 



5S J 







i 



8 



-a 

 PI 



M 

 1—* 



fl 



to ^ 



TO 



m 

 ^-» 



'a 



§ 

 M 



en - « 



1 



1 



a 

 

 



^1 



g 



■ss 



t-( t*- 



reentage of 

 ch Constituei 



St 









^ opi 



P 



5 p5 



M 



<D 



s« 



S cs 5 



a),<5 





W 



^•^ ca 



w 



<itss 



^ 



Pi 



(^S, 



P^WcS 



A^MhI 



SiO, 



45.73 



12.78 



37.09 



12.72 



45.38 



36.77 



33.41 



26.37 



73.64 



AlA 



13.48 



9.10 



13.19 



8.22 



13.38 



13.08 



9.11 



31.81 



68.19 



FeP 



11.60 



8.75 



35.69 



28.25 



11.51 



35.39 



0.00 



100.00 



0.00 



CaO 



9.92 



4.37 



0.41 



0.02 



9.84 



0.41 



9.71 



1.32 



98.68 



MgO 



15.40 



8.65 



0.57 



0.20 



15.28 



0.56 



15.09 



1.19 



98.81 



NajO 



3.24 



Not det. 



1.75 



1.00 



3.21 



1.73 



2.64 



17.54 



82.46 



K2O 



0.47 



it 



0.33 



0.20 



0.47 



0.33 



0.35 



22.69 



77.31 



HP 



0.94 



0.94 



11.83 



11.83 



0.93 



11.73 



0.00 



100.00 



0.00 



Total 



100.78 



44.59 



100.86 



02.44 



100.00 



100.00 



70.31 







Gain. 



