PETROLOGICAL ABSTRACTS AND REVIEWS 173 



mineral may well represent a corroded apatite of a form not uncommon, 

 and its occurrence surrounded by magnetite is indicative of the same 

 mineral. Unless the fragments were large enough to permit of absolute 

 determination as zoisite, the reviewer is inclined to think the original 

 identification correct. 



Becke, F. Ueher den Monzonit. Festschrift C. Doelter. Dres- 

 den and Leipzig, 1920, 1-14. Fig. i. 

 Monzonite, originally a collective name for all the different rocks 

 found on Predazzo and Monzoni, has been variously used. Becke gives 

 the following definition: Monzonite is a plutonic rock of granular 

 texture. Its essential constituents, in the order of their crystallization, 

 are magnetite, augite, hornblende, biotite, plagioclase (average composi- 

 tion andesine), and perthitic orthoclase. Small amounts of quartz or 

 aegirite-augite or nephehte may occur. Accessory minerals are apatite 

 and titanite. The dark and light constitutents, also the orthoclase and 

 plagioclase, are of approximately equal amounts. Chemically the An: 

 Ab: Or ratios are about 20:45:35; and the Ca:Mg:Fe = 3o:3o:40. 

 SiOz fluctuates around the point of saturation, so that quartz or a f eld- 

 spa thoid may occur in small amounts. Becke objects to the use of the term 

 monzonite as apphed to rocks of the "Pacific type." The sihca content 

 must be below 63-64 per cent. The term thus used is dependent upon 

 the chemical composition. Used in the foregoing sense, many rocks 

 described as quartz-monzonites are not such at all. 



Benson, W. N. "Report on the Petrology of the Dolerites 



Collected by the British Antarctic Expedition, 1907-1909," 



Geology, Vol. II, of Shackleton's Report. London, n.d., 



153-60. Figs. 6. 



Dolerites, in this report, are rocks composed essentially of basic 



plagioclase and pyroxene, with varying amounts of quartz. Following 



British usage they are called dolerites (diabases. United States). Since 



the name was originally given by Hauy to coarse-grained basalts, the 



use of the expression aphanitic dolerite seems anomalous. Several 



analyses, recast in the C.I.P.W. system, are given, and the rocks and 



component minerals are described in detail. 



