194 
iMitcham. 
Macroscopic characters V егу coarse grain- 
ed and intensely hard rock, composed of rounded and angu- 
lar grains of different materials firmly cemented together. 
Fractures across and not around individual grains, fractured 
surface being very vitreous. Chiefly colourless quartz, toge- 
ther with a little which is smoky and still less opalescent. А 
good deal of fresh-looking, pinkish felspar and still more that 
is strongly kaolinized. Considerable number of rock frag- 
ments, mainly liver-coloured cherty rock and greenish schist. 
Microscopie charact en s.—Texture very 
coarse. About 40 per cent. felspar, rest mainly quartz. 
Quartz in completely angular grains in optical contact. All 
show evidence of having been originally rounded grains. ‘The 
present form is due to secondary deposition of quartz upon 
the clastic grains in optical continwity with the original (reju- 
venescence of crystals). Inclusions not very abundant. 
Mostly liquid and gas cavities, the former with moving 
bubbles. These are mostly irregularly distributed through 
the quartz, but long lines of inclusions evidently occupying 
secondary solution planes pass without interruption through 
two or more contiguous grains. This indicates that the rock 
has been buried to a very considerable depth below the earth's 
surface. A few individualised inclusions consisting of small 
mica plates and zircon (?) crystals are also present. Not 
much evidence of severe strain. A little undulose extinction 
has been induced, but only very rarely has a quartz grain 
been completely shattered. 
Felspars are of three distinct types: --а, Albite, in clear 
and undecomposed idiomorphic sections; 0, microcline, fresh 
and somewhat idiomorphic; с, orthoclase, also fairly idio- 
morphie, but very much kaolinized. One very remarkable 
feature about the microcline is the very noticeable develop- 
ment of secondary felspar in optical continuity with the 
material of the originally rounded grains. Sometimes the 
rim shows no trace of twinning, but in other cases the twin 
lamelle of the original grain are continued without inter- 
ruption in the rim. 1 
Composite grains more numerous than they appear to be 
macroscopically. Many of them are evidently composed of 
reef quartz, others of a finely granular aggregate of quartz 
and microcline (probably gneissic), others of an excessively 
fine-grained, cloudy, quartzose rock (chert), and a few of 
fine-grained micaceous schist. 
A little barytes is present in small radial aggregates, but, 
considering the comparative abundance of this mineral in 
