143 



Nearer Mount Crawford are cyanite and rutile schists, and 

 occasional reefs containing beryl, from which, no doubt, 

 some of the gem fragments in the gravel originated. 



The placer formation contains rounded pebbles and 

 boulders of quartz, some of which are brilliant, clear, and 

 flawless. The finer material consists of gravel containing 

 rounded grains and pebbles up to 2 in. in diameter of rough 

 blue corundum (sapphire), much crystal rutile, and coarse 

 gold, besides small fragments of a variety of gem-stones, as 

 detailed below. The whole is bound together by a tough 

 clay. 



Corundum. — About 6 ft), weight of waterworn pebbles 

 of sapphire were examined. These are much cracked, and 

 not of gem quality. In microscope section they are shown to 

 be composed entirely of corundum, though many individuals 

 contribute to the aggregate. A strong tendency is shown 

 for the individuals to arrange themselves parallel in the direc- 

 tion of their hexad axes. The cornflower-blue colouring is 

 strongest on the periphery of the crystals and decreases 

 within, the centres being frequently colourless. One speci- 

 men is portion of a large crystal, |-in. in diameter, and shows 

 deep-blue edges bordering a light-pink coloured centre. 



Small gem-quality fragments of both the sapphire and 

 the light-pink variety were also found. Several specimens of 

 these latter are specially good. The best stone found weighed 

 just over one carat, and is of a pale-rose-pink colour. This 

 pale variety of ruby is sometimes called female, nihy, 

 to distinguish it from the masculine ruby of deep pigeon- 

 blood-red colour. Similar stones, one weighing half -carat 

 and four others of less size, were isolated. All show water- 

 worn outlines. The specific gravity of the several types of 

 corundiim is remarkably uniform, being 3'8. 



A flat cleavage chip was found, about 1-16 in. thick and 

 I in. in diameter, with hexagonal outline, and divided into 

 sectors by bluish lines radiating from the centre. This fea- 

 ture leads to the production of asterism. 



Topaz. — Small fragments of golden topaz; none, how- 

 ever, suitable for cutting. About forty of these, averaging 

 quarter-carat, were examined. Several were useful fragments 

 of clear wliife topaz, one of which weighed one carat. This 

 latter is particularly good stone. They have waterworn 

 surfaces. 



Aquamarine. — About fourteen fragments of small size 

 up to one-third carat, of a pale-blue colour. They show a 

 splintery surface. 



Chrysoberyl occurs abundantly as small fragments of a 

 honey-yellow colour. These exhibit a sharp, fractured sur- 

 face. They were met with up to about half-carat in weight. 



