314 |OURNAL OF SCIENCE. 
Orthoclase.—Although occurring in greater or less abundance 
in both the E. and W. and N. and S. layers, as well as the dykes, 
determinable crystals of this feldspar have as yet been found by 
Mr. Docherty in only one of the E. and W. layers. All those I 
saw were distinguished by dominant growth in the direction of 
the clinodiagonal axis, and two deserve some notice on account 
of their uncommon mode of development and other peculiarities. 
No. 1 crystal: This is nearly 2% inches long, and slightly over 
1 inch in diameter. Its form is shown in Fig. 6, representing the 
combination of the planes: 0 = OP(OOI1); m = o Poo (Old) ; 
t+ £ =o P(ito)s p.= Prt) sx = Pool 101) ay ree 
(201); z = %P(112). The angles to determine these symbols 
could only be measured with the hand goniometer, and con- 
sidering the roughness of the planes, especially of the prism and 
positive hemi-pyramid, agreed very well with those found by 
accurate measurement. The rather rare positive hemi-pyramid 
z = ¥%P was well determinable by the angle z :o0 = 150° 30 
(150° 52’ Dana), on account of the planes o and z being smoother 
than the rest. It occurs hemihedrally, as no trace of it is visible 
in the lower front quadrant, where itshould appear. The planes 
p are very uneven, the projections and depressions having a 
glazed or fused-like appearance. At the back end, where the 
crystal was broken off its support, a tolerably plain cleavage is 
observable parallel to the prism-plane t’, and this portion further 
shows that the mass of the crystal is abundantly impregnated 
with copper pyrites and pyrrhotite, ragged portions of which are 
also protruding from the basal and clino-pinacoid planes ; a few 
small scales of black mica can also be seen in the mass. No. 2 
crystal: This is about 1 inch long and 34 inch in diameter, and 
shows the same combination of planes as crystal No. 1, with the 
exception that the hemi-pyramid z is absent. In its mtode of 
development it differs from No. 1 in that the basal and clino- 
pinacoid planes are of equal size and through the nearly equal 
growth of the prism-planes t and t’ and of the positive hemi- 
pyramid p upto thesmall orthodome y (2 Po), whilst the ortho- 
dome x(Po ) forms only a narrow truncation of the edge p:: p, 
the crystal has very much the appearance of one of the tetragonal 
system (see fig. 73) resembling Wernerite of the scapolite group. 
In other respects it is similar to No. 1, not only by having glazed 
or fused-like depressions and projections on the pyramidal faces, 
but also by showing at its broken end that it is thickly impreg- 
nated with copper pyrites and pyrrhotite, which latter forms also 
thin coatings over parts of the basal and clino-pinacoid planes, 
whilst black mica scales project from nearly all the planes. 
From what Mr. Docherty states there is no doubt that 
opening of the layer at the place where the specimen came from 
would reveal far finer crystallizations of orthoclase than those 
described. 
GEORGE H. F. ULRICH. 
ee nt 
