MINERAL OCCURRENCES AT DUSKY SOUND. | 313 
planes were not bright and smooth enough) that the angles of 
the prism-planes conform well with those in the orthodiagonal 
zone of epidote—the apparent square prismatic planes being, 
according to Mohs’ position, oP(oo1) ; ° Po (100) and the re- 
placements of the vertical edges: Po(101).—P (101); ac- 
cording to Miller’s position, respectively (102) (100), and (101), 
(001). The orthopinacoid is the plane to which the cleavage 
goes parallel. The correctness of this determination of the 
mineral as epidote has since been proved by the following re- 
sults of an analysis by Mr. T. Butement :— 
SiO; - - = 36.33 
Ail, O, = - 5 28.81 
eS : 7 2 9.15 
c - - : 1.05 
Ca © = : = Q221 
Mg O - - - 0.16 
isha S, = = - 0.9 
Total, 98.61 
Whewspec. erav. of this epidote. was found to be 3.454. 
The mineral evidently occurs in great abundance in the quartz 
reef, and is rather brittle, as regular “epidote sand,’ of which 
Mr. Docherty’s collection contained a sample, can be washed out 
in quantity from the detritus in the neighbourhood of the reef. 
2nd Variety.—This is not so abundant as the one just de- 
scribed. It occurs in one of the N. and S. layers, and is of a 
dark brownish-grey to light greyish-brown colour, forming pris- 
matic crystals up to 2 centim. in length and 8 mm. in diameter, 
which penetrate orthoclase or project from cavities in it. The 
prisms have in cross section an irregular outline, are longitudinally 
deeply furrowed or striated, and show no determinable faces at 
the ends, appearing, as it were, as if gnawed off. In fresh fracture 
they have a strong greasy lustre, quite as strong as Elacolite, for 
which they might easily be mistaken if it were not for their 
irregular outline and behaviour of samples before the blowpipe. 
A peculiarity observable with respect to almost all the longer 
prisms is that they are curved and frequently broken crossways, 
in most cases so that the severed parts are slightly displaced and 
the fracture cracks open, indicating strain or contraction after 
formation. This variety was found to have a spec. grav. of 
3.472, and a quantitative analysis of it by Mr. F. Butement gave 
the following results :— 
mi ©, - - ay 26:27 
sue OF 7 3 f 23.70 
saat - - - 13-35 
she = - - 0.82 
Ca O : ; : 24.97 
Me O - - - 0.32 
rH - - = 0.24 
Total, 99.73 
