482 PROCEEDINGI^ OF TUB NATIONAL MUSEUM. vol. 57. 



birefringence, and approximately parallel extinction. These are too 

 minute for their character to be determined, but they bear some 

 resemblance to the minute rutile needles which make up the so-called 

 sagenite nets. The diopside phenocrysts are rare and usually only 

 small grains and patches of unaltered diopside occur, embedded in a 

 mass of chloritic alteration products. The rock is a very typical 

 minette. 



A specimen from halfway between the two oreshoots on the 600- 

 foot level is a holocrystalline very fine grained nonporphj^ritic ag- 

 gregate of minute laths of feldspar and chlorite in shreds. The rock 

 is greatly altered and now consists chiefly of chlorite. The original 

 ferromagnesian mineral was clearly biotite although no vestige of 

 unaltered biotite now remains. The feldspar grains, which are 

 very minute, are untwinned and are probably orthoclase. The fabric 

 is regularly dotted with grains of iron ore. Large patches of in- 

 filtrated calcite occur and inclusions of clear quartz are abundant. 

 In some cases these inclusions are a single crystal individual but more 

 frequently they are aggregates of interlocking grains, quite evidently 

 fragments of quartzite. The quartz exhibits rolling extinction and 

 other strain phenomena. These inclusions have no reaction rims. 



Another specimen from the middle oreshoot on the 900-foot level 

 is fine grained, holocrystalline, and fairly fresh. It contains numer- 

 ous well-crystallized tablets of pleochroic brown biotite scattered 

 through a ground composed almost entirely of alkalic feldspar hav- 

 ing a trachytic texture from being composed of bundles of lath- 

 shaped fibers sometimes curved and divergent and yielding rolling 

 extinction. Iron ore in the usual small euhedrons is scattered 

 throughout the fabric of the groundmass. Grains of augite exceed- 

 ing the largest biotite phenocrysts in size occur at frequent intervals. 

 These seem much shattered and irregular pieces seem to be detached 

 portions of much larger individuals. They show well-defined cleav- 

 age but are much cracked and uralitization has progressed along 

 cracks until now only grains of unaltered augite occur embedded in a 

 mesh of alteration products. Occassionally one of these augites 

 shows a sharp crystal boundary lined with grains of iron ore. In 

 one place an inclusion of quartz — a single large rounded crystal 

 individual — has a well-defined rim zone containing feathery crystal- 

 lizations of magnetite. Infiltrated calcite is common. 



A specimen from betvv^een the 1,400 and 1,600 foot levels is a mod- 

 erately fine-grained rock consisting of biotite phenocrysts of the ordi- 

 nary type in a ground of orthoclase which is now badly sericitized. 

 Iron ore forms scattered grains and apatite is present in stout well- 

 formed crystals. Calcite is very abundant and is m places inter- 

 grown with a green secondary mineral resembling chloropal. The 

 section contains numerous inclusions of clear quartz having border 



