Mabshall. — Boulders in Triassic Conglomerate, Nelson. 469 



C 278. — Granite. White, coarse-grained. Quartz white. 

 Biotite plates not present. Feldspar white. 



Quartz clear, in large grains, on the exterior of which there 

 is often an intergrowth of feldspar. Feldspar chiefly ortho- 

 clase, rather decomposed, much intergrown with quartz, even 

 in the interior of large crystals. Cloudy with minute decom- 

 position products. No ferro-magnesian minerals. A few 

 irregular grains of sphene, showing distinct pleochroism. 



C 279. — Granite. Dull-pink. Porphyritic quartz. Biotite 

 small. 



Section generally similar to C 277, but quartz rather 

 coarser. In places microgranitic structure, but generally 

 micrographic. Brown biotite more abundant than in C 277, 

 and magnetite much pierced by crystals of apatite. No 

 sphene or zircon visible. 



C 280. — Granite. Large white crystals of porphyritic 

 feldspar in pink fine-grained base. 



Section similar to C 275, but coarse-grained. Feldspar 

 includes orthoclase, albite, and microperthite twinned in the 

 usual way. Large flakes of brown biotite with apatite 

 needles. No hornblende. A little magnetite and sphene. 



C 28L — Diorite. Dark hornblende in irregular crystals. 

 Grey feldspar. 



Feldspar crystals allotriomorphic, showing twinning on 

 albite and occasionally on pericline laws. Extinction angle 

 30°, indicating an acid labradorite Much decomposed into 

 comparatively large crystals of epidote, muscovite, quartz, 

 and "garnet." Hornblende plentiful in light-green crystals 

 pleochroic from green to pale-yellow, occasionally twinned. 

 Much intruded by various inclusions for the most part origin- 

 ally feldspar and apatite. Now decomposed like the surround- 

 ing feldspar. No magnetite or other accessory minerals. 



C 282. — Porphyry. Feldspar phenocrysts green. Base 

 greyish-brown. 



Phenocrysts of orthoclase idiomorphic, twinned on Carlsbad 

 law ; much decomposed, apparently into sericite. Smaller 

 phenocrysts of epidote, but crystals not optically single, but 

 aggregates. Form similar to hornblende, from which the 

 mmeral is derived. Base rather coarsely felsitic, but no trace 

 of original microlites, so pi'obably originally a glass. Fel- 

 sitic matter apparently composed of feldspar and a decom- 

 posed ferro-magnesian mineral. Magnetite in fairly large 

 .grains not infrequent. 



