22 MINING INDUSTRY. 



The mass is of a prevailing cold-gray color. Mount Butler shows upon its 

 eastern front clouded stains of red, which are probably the traces of solfataric 

 action. There are discernible through the general gray mass occasional len- 

 ticular portions of almost jetty black, but they are unimportant features. An 

 attempt to develop parallel planes is observable on the slopes of Mount 

 Davidson, and a general conoidal structure, suggesting its alliance with the 

 granitic family, characterizes the structure of Mount Butler. Weathering has 

 developed prominent lines, which traverse the parallel north and south 

 plains, and seem to be a lithological rather than a structural feature. The 

 syenite is exceedingly dense, of high specific gravity, and so tough as to 

 break with great difficulty under the hammer. The shingle, or de'bris, 

 which covers almost its whole surface, is formed in sharp, angular frag- 

 ments, whose great hardness effectually prevents disintegration, so that 

 there is little tendency to decompose, and, in consequence, almost no sye- 

 nitic soil. The rock is composed of orthoclase, green hornblende, and 

 titanic iron, having, as an occasional accompaniment, oligoclase and epi- 

 dote. The average rock is a crystalline blending of orthoclase and fibrous, 

 broken particles of green hornblende ; the prevailing purplish-gray of the 

 former toning the whole rock. The hornblende crystals are chiefly grouped 

 about small nuclei of titanic iron. The approximate proportions are, ortho- 

 clase, 75 ; hornblende, 24 ; titanic iron, 1. They were evidently of synchronous 

 origin — the hornblende penetrating the feldspar in certain cases, and in others 

 the reverse. Each prism of the hornblende contains within it more or less 

 crystalline particles of the feldspar, and, with the exception of certain porphy- 

 ritic portions, the feldspar invariably contains some fibrous particles of horn- 

 blende. At rare intervals, brilliant, flat crystals of black hornblende occur, 

 cutting both the orthoclase and green hornblende. Oligoclase traverses the 

 ordinary syenite in veins from the thickness of a line to a foot, usually segre- 

 gated from the orthoclase rock by an accumulation of microscopic hornblende 

 crystals. Oligoclase also occurs in lenticular bodies, scattered at intervals 

 through the entire mass, within which the hornblende groups itself in radial 

 forms, and in each case penetrates the ohgoclase. We have, then, the follow- 

 ing paragenetic succession of constituents : Titanic iron ; orthoclase and green 

 hornblende ; fibrous, radiating, oHve-colored hornblende ; ohgoclase ; and, 



