263 



greenish in colour, and surface specimens are always turbid 

 and much cracked and discoloured. The crystals are usually 

 bounded by 1010 faces with irregular ends. In one case the 

 1010 faces were bevelled by 2130 faces and the ends 

 "terminated by definite basal planes. The most notable 

 feature, however, is the great size to which they attain. The 

 fragments of a crystal weighing 100 lb. were recovered from 

 one outcrop. 



4. Loadstone. — Slugs of highly-magnetic polar magnetite 

 occur weathered out along the outcrop of a basic intrusion in 

 the Pre-Cambrian belt about one mile to the north-east of 

 the Woman-in-White Mine, Boolcoomatta. 



5. Monazite.- — This mineral occurs in notable quantity in 

 association with corundum in the corundum-mica-schist be- 

 tween Mounts Pitt and Painter, in the Flinders Range. This 

 formation is within two miles of the great lode culminating 

 in Mount Gee, associated with which are the several radio- 

 active minerals already exhibited at a meeting of this Society 

 — namely, autunite and torbernite, with less-frequent 

 zeunerite, gummite, carnotite, etc. The nionazite-bearing 

 rock in question outcrops as an irregular patch about a 

 quarter of a mile in diameter and is intersected by a gorge. 

 The neighbouring rocks have been shown to be Pre-Cambrian, 

 and are chiefly volcanic. (Tide Aust. Ass. for Adv. Science 

 Report, 1911.) The origin of the formation appears to 

 have been the result of the action of gaseous and liquid 

 magmatic solutions (pneumatrolysis) upon the surrounding 

 rocks. Such a conclusion is supported by the nature of the 

 mineral association, by the coarseness and irregularity of the 

 crystallizations, and by the presence of much tourmaline, 

 apatite, and monazite. The absence of silica, and the abund- 

 ance of mica, cordierite, and the like, show that agent was 

 doubtless rich in hydrofluoric acid. Massive formations of 

 fluor spar and remarkable crystallized quartz formations else- 

 •where in the neighbourhood (e.g., at Mount Gee) further 

 •support this theory. On this line of reasoning the Mount Gee 

 formation is to be regarded as a later phase (further from 

 the magma hearth) of pneumatrolysis which, in the first 

 place, had effected the development of the corundum-mica- 

 schist belt containing the monazite. Monazite is everywhere 

 present in the corundum-schist, but in very variable amount. 

 Here and there it is visible to the naked eye in the hand 

 specimen, and aggregates up to half an inch in diameter have 

 come under notice. It is usually embedded in or surrounded 

 "by the leaves of the mica, but where black tourmaline is 



abundant is often embedded in the tourmaline. Crystalline 

 facets are commonly shown on the grain-like individuals. The 



