part 4?] 



MATERIAL OF'JiUNTEll PEBELE-13EDS. 



329 



be observed, but false bedding is a marked characteristic of this 

 formation. 



Tiie following simple minerals, aggregates, and compound grains 

 have been found : — 



Simple Minerals. 



Grarnet 



Fluorspar... 



Magnetite 



Quartz. 



Tourmaline 



Apatite 



Ilmenite . . . 



X X 

 X X 

 XX 



XXX 

 X 



XXX 



P^-rrhotite 



Zircon 



Eutile 



Anatase . . 



. X X 



XXX 

 . X X 

 X 



Staurolite XXX 



Sillimanite X 



Biotite X 



Muscovite. 

 Orthoclase. 

 Plagioclase. 

 Microcline. 

 Kyanite 



Heavy minerals marked thus 



X 



X X 



occurrence, 

 frequency. 



XXX abundance. 



Mineral aggregates and compound grains include: — 

 Shimmer-aggregates, . chloritic aggregates — probably; felsite, 

 cryptoperthite, quartzite, leucoxene, quartz — in addition to decom- 

 posed iron-ore, vein-quartz, chert, and schist. 



Per cent. 



TQuartz 72 



Estimated general constitution j Felspar 25 



^ of Pebble-Bed sand | Heavy minerals 0*25 



L Various 2-75 



III. Descriptiox of some of the Simple Mineeals. 



Garnets, mosth' of a characteristic pink, appear to be fairly 

 evenly distributed, though they are not very plentiful. Spherical, 

 irregularly-rounded, and angular grains are present, the last-men- 

 tioned being the least frequent. Most of the garnets are isotropic, 

 while a few have been observed to be optically anomalous. The 

 largest grain noted was 0-40 mm. in greatest diameter. Generally 

 they are smaller, some considerably so. 



Fluorspar is fairl}^ common. The grains are usuall}- angular, 

 isotropic, and colourless. No grains having a greater length than 

 0*30 mm. have been noted. 



Magnetic minerals ^ are fai];ly frequent, and include mag- 

 netite. Other magnetic gi-ains of a yellowish-bronze colour are 

 probably pyrrhotite. 



Quartz. — In form these grains are subangular, angular, and 

 well-rounded : the first constitutes the bulk of the quartz. The 

 biggest grains, comparatively few^ in number, are often apparently 

 perfect spheres. The grains are frequently more or less corroded. 

 Growths of secondar}^ silica on the grains have not been met with. 

 Undulose extinction and other evidences of strain are frequent. 



^ These minerals were removed with an ordijiary magnet from samples of 

 uncleaned sand. 



