OCCLUSION OF IGNEOUS ROCK 



421 



Remnants of most or all of these minerals abound in these 

 rocks, although, in large part, they are more or less altered and 

 have passed into very minute particles, fibers and scales. In 

 investigating the mineral constitution of the Hoboken serpen- 

 tinoid, magnetite was separated in the manner already stated 

 and weighed ; pleonaste calculated from estimated volume, on 

 part of the alumina ; and chromite from percentage of chromic 

 acid found in the analysis. 



The presence of carbonates in this rock having been shown 

 by-Newland's observations and my own, the loss in Goodell's 

 analysis was fairly referable to the undetermined amount of 

 carbonic acid ; from this the carbonates were estimated, chiefly 

 dolomite, with a little calcite and perhaps hydromagnesite. The 

 remainder of lime supplied the basis for determination of the 

 lime-magnesia-iron silicate of a composition intermediate be- 

 tween diallage and augite ; for this the analysis of leucaugite 



Chemical Composition of Hoboken Serpentinoid. 



Mineralogical Constitution. 



Magnetite .50 



Pleonaste 08 



Chromite 69 



Chlorite ' 3.15 



Dolomite with calcite and 



hydromagnesite 3-53 



Diallage with amphibole 



and bastite 58.10 



Serpentine with talc 18.45 



Brucite with bronzite 8.97 



Water 6.53 



100.00 



«o 

 ^ 







n 



k ■ 



u 





9^ 





9^ 

 ;3- 















.35 



.15 











•05 



.01 







.02 



— 



1.04 



.60 



.44 



— 



.21 



.16 



.04 

 •94 



— 



— 



— 



— 



— 



— 



.77 



1.07 



! 28.23 

 7-63 



.40 

 .24 







5-44 



•47 

 •47 



8.17 

 7.62 



14.46 



— 



— 



— 



— 





6.19 









.41 — 



93 

 49 



78 



53 



1.69 



from Amity, New York, by Harrington, was selected as most 

 suitable, with substitution of ferric oxide for alumina. From 

 the remainder of silica, the jimount of serpentine was calculated, 

 on the figures of Garrett's analysis of marmolite from Hoboken. 

 From the balance of magnesia the amount of brucite was 

 estimated. The remainder of water signified the hydration of 

 the greater part of the diallage molecule in the form of the 



