94 
Epidote Rock (Altered Granite). 
Plate xvii., fig. 4. 
Locality. — Musgrave Ranges, Titania Spring. 
MacroficopicaU i/.—X granular rock, composed of clear 
quartz and white, clouded felspar, traversed by veinlets of 
epidote, the small columns that build uj^ the bulk of the epi- 
dote standing with their long axes at right angles to the 
bounding lines of the veins in the section. 
Microscopically. — The texture of this rock, though no 
doubt originally holocrystalline, has been obscured by the 
secondary secretion of epidote : the rock has, moreover, suf- 
fered considerably from crushing. 
The felspar is orthoclase, though little of its primary 
characteristics remains, it having^ yielded to metamorphism by 
transformation into epidote. Intermediate stages of this con- 
version are general. 
The epidote, which is light greenish-yellow in colour, 
covers fully three quarter parts of the section, as aggregates 
of irregular, elongated, and columnar individuals. The strong 
relief produced by the total reflection at the border of the e|Di- 
dote is characteristic, and the cleavage is conspicuous in the 
larger individuals only. 
An imperfect "cross-hatched" appearance is here and 
there visible on the faces of the felspar under crossed nicols. 
This is an extreme case of 'strain shadowing" as a result of 
pressure. 
Hematite (micaceous) is present as dark reddish-brown 
(by transmitted light), hexagonal plates, presenting a slight 
metallic lustre by reflected light. The perfect forms range 
up to "27 mm. in diameter, and the adjoining minerals are 
invariably stained red by iron pigment for some distance 
around. 
Gneiss. 
Plate xviii, fig. 1. 
Locality. — Indulkana, Krupp Hill West. 
Macroscopically. — A fine-textured gneiss, consisting 
essentially of quartz (colourless), felspar, and biotite, the last- 
named being arranged in a more or less parallel manner with- 
out the production of distinct, continuous planes of foliation 
( Quincuncial Btriicturc). It is traversed by shattered veinlets 
of quartz. A green accessory mineral (epidote) is developed 
as irregular particles and patches throughout the rock, im- 
parting a faint yellowish-green tint to the rock mass. 
Microscopically. — Texture finely crystalline, granulitic, 
with faint parallelism in the arrangement of the constituent 
minerals. In parts a feeble centric structure is discernible. 
