186 A. T. ULLMANN. 



A NEW MINERAL. 



By A. T. Ullmann, 



Chief Assayer, Chillagoe Company, Chillagoe. Queensland. 



[Read before the Royal Society of N. S. Wales, June 5, 1912.^ 



The mineral which forms the subject of the present note 

 was found in the Christmas Gift North Mine, Chillagoe, 

 associated with cerussite in a gossan formation, some of 

 the crystals being studded with small crystals of pure 

 cerussite. I have named the new mineral Chillagite. 



The crystallisation appears to be tetragonal, the form is 

 tabular and the diaphaneity translucent. 



Colour: — Straw or lemon-yellow, sometimes brownish. 



Structure : — Lamellar. 



Hardness: — 3*5. Very brittle. 



Specific gravity : — 7*5. 



Composition 1 : — Tungstate of lead and molybdate of lead r 

 PbO 54*25%, W0 3 28-22%, Mo0 3 17*52%. 



Formula:— PbO W0 3 + PbO Mo0 3 . 



Before blowpipe — Microcosmic salt bead yielded olive- 

 green in O.F. On charcoal alone, it fused easily, yielding 

 a yellow incrustation of PbO near the assay, and a bluish 

 one on the outer edge of Mo0 3 . 



With Na 2 C0 3 on charcoal a prill of metallic lead was 

 produced. 



Treatment with HOI and HN0 3 leaves a yellow residue 

 of tungstic acid. A small quantity heated with a drop of 

 H 2 S0 4 on a porcelain cover yielded a deep blue colouration 

 due to molybdic acid. 



1 See also report of the Queensland Government Analyst, Queensland 

 Government Mining Journal, xiii, Feb. 1912. — Eds. 



