705 
crystalline. The edges of the partings are still jagged, when highly magnified (i-inch 
objective), as they were the day they separated. On the other hand, the tourmaline 
in the Cooktown granite is highly granular, and the small prisms by no means sharp. 
No. 250. Mount Bismaeck, Coolgarba (Queensland). 
A. G. Maitland’s Collection. Sp. Gr. 2'G6. 
Colour, dark-brown. Fine-grained, almost mierogranitic. Quartz, hornblende, 
with epidote in grains, plagioclase and orthoclase. 
Section . — Quartz is hardly granulitic, owing to the epidote, which is interstitial. 
But for this it would fulfil the definition — viz., “ In approximated allotriomorphic grains, 
small, of nearly the same size, and independently oriented.” 
Bare mica; in one case it is fibrous, much broken up into septcc between 
crossed nicols, the ends of the fibres frayed out, the whole slightly curved in the form 
of the letter 8. 
No apatite or magnetite. 
No. 267. Derwent Creek, Coolgaeea (Queensland). 
A. G. Maitland’s Collection. Sp. Gr. 2‘718. 
Colour, dirty red. These rocks are not true granites, and, according to Professor 
Hutton’s system, would bo placed iu the elvanite group, as they consist of mierogranitic 
orthoclase and quartz, with porphyritic crystals of quartz and orthoclase, and sparsely 
distributed hornblende, or perhaps mica. 
Section . — The quartzes are generally allotriomorphic, and often the felspar and 
quartz are in a crystalline-granular state — pegmatitic (graphic-granite). Eutley would 
probably class these two rocks as haplites. The pegmatitic quartzes carry the usual 
inclusions, but they are minute, and a great many are mobile. The inclusions are not 
arranged in lines, but occur without system, and, as it were, haiihazard ; while in the 
porphyritic quartzes the inclusions are arranged much more systematically, being 
generally strung together in lines, which, however, bear no constant relation iu their 
direction to the crystallographic or any other axis. 
The felspars are finely fibrous. One single example occurs of plagioclase. It is 
too much altered to classify, but it is distinctly banded ; and the angles of extinction, right 
and left of the twinning planes, are — right, 10° 40'; left, 15° 30'. 
The fibres cross at an angle of 46° 30'. Some of these fibre-spectra cross each 
other at right angles, and are suggestive of mierocline, but the felspars are all so opaque 
that their optical properties are not discernible with any precision. Unfortunately, in 
the three slices beside me of this rock, the hornblende or mica is absent. One or the 
other, however, occurs, or perhaps both may occur, as accessory minerals visible to the 
naked eye, in the hand specimens. 
No. 255. Derwent Cheek, Coolgaeea (Queensland). 
A. G. Maitland’s Collection. Sp. Gr. 2'568. 
Colour, a dirty grey, with ill-defined dirty green specks of secondary origin. 
The same remarks apply to this rock as to No. 257, except that some ferrite occurs, 
and a little epidote around very minute hornblendes. 
2 w 
