172 PETROLOGICAL ABSTRACTS AND REVIEWS 



Bartrum, J. A. "Additional Facts Concerning the Distribution of 

 Igneous Rocks in New Zealand," Trans. New Zealand Institute, 

 XLIX (1916), 418-24. Figs. 3. 



Brief descriptions are given of hypersthene-basalt, troctolite, 

 granodiorite with epidote (which the writer, not the reviewer, thinks 

 primary), basalt with biotite (character of the feldspar of the rock not 

 given), hornblende-basalt, andesite, diorite, and trachyte. Most of 

 the descriptions are too brief and incomplete to permit passing judgment 

 on the names. 



Bartrum J. A., "Additional Facts Concerning the Distribution of 

 Igneous Rocks in New Zealand: No. 2," Trans. New Zealand 

 Institute, LII (1920), 416-22. Figs. 5. 



Here are brief descriptions of norite, dolerite, basalt, and hypersthene- 

 andesite, and one more extended of quartz-norite. The dolerite is 

 apparently the diabase of United States usage. The quartz-norite is 

 described as "a moderately typical norite but for two considerations: 

 first the plagioclase .... is somewhat acid, being in the main andesine- 

 labradorite; secondly, there is .... a little interstitial quartz." A 

 third objection which might have been given is the fact that besides 

 hypersthene there is abundant augite, biotite, some hornblende, and 

 "probably a third pyroxene." With a feldspar more acid than AbsqAn^o 

 why not call the rock quartz-hypersthene-diorite ? The " third pyrox- 

 ene" is described in considerable detail. All but one of its properties, 

 including orientation, agree with hypersthene, the exception being the 

 "extinction angle which was found to be from very small to 42°." May 

 this mineral not be hypersthene? The reviewer has found that this 

 mineral, in many cases, gives apparently inclined extinction in sections 

 which are cut at right angles to the principal sections and yet show only 

 one set of prismatic cleavage lines brought out by the grinding. Meas- 

 suring then from the cleavage lines, the extinction is inclined, but it will 

 usually be seen, if the stage is turned an equal number of degrees be- 

 yond the point of extinction, that there are here traces of the other 

 cleavage. Random sections cutting all three axes in orthorhombic 

 crystals do, of course, show inchned extinctions when measured from 

 cleavage lines. Zoisite is mentioned as a mineral originally identified 

 as apatite, and surprise is expressed that apatite does not occur al- 

 though the analysis gives considerable PzOg. The sketch given of this 



