152 REPORT— 1891. 



be a telluride and sulphide of lead, gold, and silver, containing 

 60 parts of lead, 7 parts of gold, and 15 parts of silver in every 

 100 parts. 



The ore is finely granular, with a lustre metallic and splen- 

 dent ; streak and colour lead-grey. Hardness, 1-5 to 2 ; spe- 

 cific gravity, 7"42. Before the blowpipe it yields a whitish 

 sublimate of tellurate of lead, and copious white fumes of 

 tellurous acid. On charcoal easily reduced to metallic globule 

 with or without soda. 



This rare mineral occurs in a quartz vein associated with 

 argentiferous galena, blende, pyrites, chalcopyrite, and anti- 

 monite. The rocks at the mine are brown and rusty-coloured 

 tufas or tufaceous sandstones, passing into coarser-grained 

 greenish-coloured tufas and breccias. In the finer tufas, which 

 are often much broken and slickensided, and then possess a 

 somewhat drossy and shaly appearance, have been found 

 a few fragments of black fossil wood, partially silicified, par- 

 tially carbonised. 



Experiments conducted at the School of Mines show that 

 the precious metals contained in the Sylvia ores cannot be saved 

 by ordinary amalgamation, and at the present time extensive 

 dressing-works are being erected at the mine to concentrate 

 the heavy ores for shipment to Europe for treatment. 



Petzite. — Eich specimens of this valuable ore are at present 

 being found in a small leader or drojrper running into the hang- 

 ing-wall of the main reef in the Nordenfeldt Mine, Thames 

 Goldfield. This mine is situated ac the head of Shellback 

 Creek, in the same class of country as the Sylvia Mine, from 

 which it is distant about a mile. 



The petzite occurs as a massive dark-blue, almost black, 

 substance, with a black streak. Hardness, about 2 ; and spe- 

 cific gravity, 8-82. Before the blowpipe it yields a metallic 

 bead with or without soda, emitting abundant fumes of tel- 

 lurous acid. 



A specimen of this ore analysed by Mr. H. Paltridge, of the 

 School of Mines, contained 4-12 per cent, of gold and 2-75 per 

 cent, of silver. 



Hexagonal Aragonite. — Among the minerals at the School 

 of Mines there are several examples of the hexagonal form of 

 this mineral, labelled from Cave Valley, Oamaru. The prism 

 is formed by the combination of three individuals about the 

 acute angle. The re-entering angles are generally filled in, 

 thus forming perfect prisms. 



Most of the crystals are incrusted with a coating of cal- 

 careous sinter ; and, judging from the character of the rock 

 adhering to some of them, they would appear to have been 

 found in the Waireka tufaceous greensands of Cretaceo-tertiary 

 age. 



