G. F. Becker — Metamorphic Bocks of California. 351 



tially metamorphosed sandstones in which, although a process of 

 recrystallization has begun, the clastic structure as seen under 

 the microscope is not obliterated but is often more or less 

 obscured. This class will be referred to hereafter for the sake 

 of brevity as altered sandstones. Granular metamorphics in 

 which metasomatic recrystallization of sandstones has trans- 

 formed the mass into a holocrystalline aggregate which, in its 

 most complex development, consists of augite, araphibole, feld- 

 spar, zoisite, quartz and accessory minerals. This class cannot 

 be sharply separated from the first or from the next following. 

 By the suppression of one or more constituents, groups are 

 formed under this class, such as metamorphic diabase, meta- 

 morphic diorite, amphibolite, etc. The third class embraces the 

 glaucophane schists derived from certain shales much as the 

 granular metamorphics are produced from sandstone. These 

 schists almost invariably carry muscovite, quartz, zoisite and 

 other minerals. The phthanites are a series of more or less 

 calcareous schistose rocks which have been subjected to a pro- 

 cess of silicification resulting in chert-like masses, which retain 

 schistoid structure and are intersected by innumerable quartz 

 veins. They usually carry more or less zoisite. Finally the 

 serpentines which have resulted in part from the direct action of 

 solutions on sandstones and in part from alteration of the 

 granular metamorphics. They cannot be rigidly divided from 

 the rocks from which they are derived, since many of these 

 contain some serpentine ; but there is also a very large amount 

 of tolerably pure serpentine in the region under discussion. 



A considerable number of minerals have been generated in 

 these rocks by metasomatic processes and weathering. These 

 are biotite, muscovite, augite, hornblende, glaucophane, labra- 

 dorite, andesine (probably), oligoclase, albite, orthoclase, quartz, 

 zoisite, rutile, ilmenite, titanite, apatite, garnet, nacrite, chlorite, 

 epidote, serpentine and chromite. Talc is known to occur in 

 the Coast Eanges but does not happen to be represented in the 

 collections for this investigation. A careful search has been 

 made in the slides for other minerals as rhombic pyroxene, anda- 

 lusite, dipyre, prehnite, allanite and zeolites, but without success. 

 Zeolites have been found macroscopically in vugs, but not as 

 rock constituents. The most interesting and in some respects 

 the most important mineral found is zoisite, which has been 

 repeatedly analyzed and tested. It corresponds completely to 

 that found by Mr. A. Cathrein in the European saussurites.* 



* Dr. T. S. Hunt was, I believe, the first to show that some saussurites were 

 largely or wholly composed of saussurite (this Journal, vol. xxvii, 1859, p. 336). 

 Mr. Cathrein showed that many of them are mixtures of zoisite aDd feldspar 

 (Groth's Zeitschrift fur Krys. u. Min., vol. vii, 1883, p. 234). Since the composi- 

 tion of saussurite is known, it does not appear desirable to retain this designation 

 for the mixture. 



