702 
NOTES. 
GEANITES. 
No. 26. Kino of Cboydox Claim, Ceotdon (Queensland). 
li. L. Jack’s Collection. Sp. G-r. 2'661. 
Colour red. Granular, allotriomorphic. Water-clear quartz, reddish felspars, 
hornblende sparse, with magnetite, epidote, and ferrite as secondary minerals. 
Quartz clear, allotriomorphic, with numerous inclusions ; some rather large with 
moving and fixed bubbles, the latter unaltered by exposure to ice, or a jet of hot air 
blown on to the section through a blowpipe whose tube was heated with a small spirit- 
lamp while the slide was on the microscope stage. A few long clear fine prismatic 
needles penetrate the quartz in no particular direction, in some cases pas.sing through 
the quartz into a neighbouring felspar. Their index of refraction must be high, for 
the needles shine out sharply with dark borders. I think they are rutile, which Teall 
as occurring in the quartz of some of the Scotch granites ; only he describes 
them in a single word as being “hair-like,”* while these needles are not triehitic. An 
actual measurement (with a Stage Micrometer, however) gave '0.3 x '0005 inch. 
Eerrite is enclosed in the quartz, amorphous, visible under the -i-inch objective. With 
the ferrite occur flecks and specks of what must be haematite, being bright orange-red 
and transparent to translucent, but they are found more in the irregular cleavage- cracks 
and fissures, pointing to secretion, from pre-existent minerals, carried on for ages by the 
infiltration of water. 
Felspars much altered, nearly opaque. They enclose dirty light-green epidote. 
Magnetite occurs once only, associated with possible epidote and chlorite, in the wreck 
of a plagioclase felspar. In ordinary transmitted light there appear long parallel cuts, 
allowing the light to pass up through a semi-opaque mass of dusty and cloudy matter. 
Between crossed nicols, these lines are parallel with an axis of extinction. Whether 
this is due to the “ aggregation of a perfectly uniform colourless substance along the 
cleavage-cracks of an orthoclase crystal,” as noted by Bosenbusch,* I cannot say. The 
structure is common in the felspars of Croydon and Charters Towers, and among other 
granites. 
Hornblende brown, showing cleavage parallel to C, generally fringed with epidote. 
If the hornblende abuts on quartz and felspar the epidote prefers, invariably, to secrete 
itself on the felspar side. A few instances of the fan-shaped groups of epidote occur, 
as drawn in Zirkel’s Petrography, j; 
No. 162. Etueeidoe Gold Field (Queensland). 
E. L. Jack’s Collection. Sp. Gr. 2'615. 
Colour greyish white. Granular, with large fresh idiomorphic felspars, often 
|--inch long, with well-marked cleavage. 
Quartz allotriomorphic, and the whole speckled with small grains of biotite. 
Very little hornblende. Both biotite and hornblende are accessory minerals. 
* J. J. Harris Teall. British Petrography, 1888, p. 324. 
t H. Roseubusch. Microscopical Physiography of the Rock-making Minerals, translated by Joseph 
P. Iddings, 1888, p. 280. 
tPerdinand Zirkel. Microscopical Petrography, in Report Geol. Explor. Fortieth Parallel 
Washington, 1876, Plate iii.. Pig. 4. 
