124 RECORDS OF THE AUSTRALIAN MUSEUM. 



tains veins and patches ot clialcopyrite. The mineral was ex- 

 amined chemically and found to he normal tetrahedrite, contain- 

 ing copj)er, antimony and sulphur ; no arsenic was detected but it 

 may be ])resent in slight amount as the quantity available for 

 testing was very small. 



Two crystals were measured ; they show the tetrahedral de- 

 velopment, the forms present being o (111), o, (1 11), c? (HO), 7i 

 (211), ?• (332). One line face of the cube was observed. The 

 crystals are of almost ideal symmetry as represented in the 6gure. 



GYPSUM. 



Mount Elliott, Gloncurry, Queensland. 

 (Plate xxxvii., fig. 5.) 



Since a short description of a crystal of seleuite from this mine 

 was published*, additionul specimens have been obtained from 

 Mr. W. T. Watkin Brown. Particularly fine are the groups of 

 large, interpenetrating crystals, in the interstices of which are 

 small well lormed crystals, suitable for goniometric investigation. 

 The large crystals seem to be without excei)tion twinned on a 

 (100) and elongated parallel to the c axis, while the smaller 

 crystals are untwinned and elongated along the a axis, by one 

 end of which they are usually attached. 



Mr. W. H. Corbould, general manager of the mine, has kindly 

 furnished me with the following particulars of the mode of occur- 

 rence. "The country rock is slate. The ore body in places is over 

 one hundred feet wide. . . At the 400 ft. level (No. IV.) the ore 

 is primary sulphide and, judging by the way the ore makes at this 

 level and the large vughs, it points to the copjjer being deposited 

 through ujirising watei's. In all the vughs there is lime. 

 Between the Nos. II. and III. levels the ore has been alteied in 

 places and even at the pre.'sent time there is a large amount of 

 chemiyal action going on, as is noticed by the heat generated. Jt 

 is between the Nos. II. and III. levels that the selenite is found, 

 not always in vughs but at times in large deposits — one face 1 

 saw was quite twenty feet long by fifteen feet high of nothing but 

 crystals It was a great sight but I regret to say it was used as 

 flux." 



*Aiuler80ii — Rec. Austr. Mus., vii. 1909, p. 276. 



