REVIEWS 435 



experiencing its most rapid growth in this country. The classic locaH- 

 ties have afforded type specimens that have woven themselves into the 

 very fabric of the science. 



The present volume sums up a wealth of published data and adds 

 much original material gained through a decade of field and laboratory 

 study. The book consists of two main divisions: the first takes up the 

 mineral species in Dana's order with physical and chemical data and a 

 list of localities for each species. While much information is repeated 

 from standard mineralogies, the compactness and completeness of the 

 data justify the duplication. All reliable and "semi-reliable" chemical 

 analyses of Pennsylvania minerals have been included. Cuts from a 

 variety of sources illustrate crystallography. In the second part of the 

 book, the localities are described by counties and townships. A valuable 

 feature of the book is the use of the Kemp co-ordinate system so that 

 by a figure of four digits any spot may be located accurately on a topo- 

 graphic atlas sheet. The minerals under each locality are listed by 

 paragenetic classes. 



While considerable emphasis is placed upon paragenesis, economic 

 geologists would probably have liked to see this phase given even more 

 attention. The class " hydrothermal deposits," for example, is not 

 subdivided, and veins of high and low temperature are grouped together. 

 For some localities data are doubtless lacking, but for French Creek, 

 Cornwall, and many other deposits, the author has sufficient first-hand 

 acquaintance with conditions to have given his readers some interesting 

 observations on mineral sequence. 



An introductory chapter on "Origin and Occurrence of Minerals" 

 gives a concise resume of geologic processes. The statement (p. 4) that 

 kaolin may be formed by hydrothermal metamorphism may be ques- 

 tioned. Tennantite is classed as an arsenide, although enargite is cor- 

 rectly described as a sulpharsenate. The growing number of believers 

 in the hypogene origin of much bornite and some chalcocite would object 

 to the omission of these minerals from the list of primary sulphides. 

 Pyrrhotite is a serious omission from the list of primary iron minerals. 



It is interesting to note that the author places rhodonite and tephroite 

 ainong dynamic metamorphs (Iron Manganese Zinc Deposits) and not 

 among contact or hydrothermal minerals, a viewpoint rather in accord 

 with that of Palache,^ who has made exhaustive studies of the minerals 

 of Franklin, New Jersey, than with the recently published discussion by 

 Ries and Bowen.^ 



^ Unpublished discussion. 



* "Zinc Ores of Sussex County, New Jersey," Econ. GeoL, Vol. 17, pp, 517-71. 



