18 G. CHEISTIAN HOFFMANN ON A SPECIMEN OF 



Native platinum 97'963 



Gold 0-225 



Pyrite 0-219 



Eock matter 1-593 



100-000 



The platinum was in the form of grains and pellets, varying in size from half a 

 millimetre to eight millimetres in diameter, and in weight, from three milligrams to eight 

 decigrams. The grains measuring less than one millimetre constituted but a very small 

 proportion of the whole ; there were only a few pellets measuring five millimetres, and 

 but two measuring eight millimetres ; the bulk of the material being made up of grains, 

 A'^arying in size from one to four millimetres in diameter. The grains, which were very 

 much rounded off, as though from attrition, had a lead-grey color and sub-metallic lustre, 

 they were all more or less tarnished, and the greater number contained inclusions of 

 chromite. A certain proportion of the same proved to be readily attracted by the magnet, 

 and of these, all such as were tried were found to possess polarity. After treatment with 

 dilute hydrochloric acid, which removed a little iron, the grains had a steel-grey color 

 and metallic lustre. The particles of foreign matter having been carefully eliminated, the 

 material, as a whole, was found to have a' specific gravity^ of 16'656. 



The ore was separated by means of the magnet into two distinct portions, a non- 

 magnetic and a magnetic; the latter constituted Si'SS per cent., by weight, of the whole 



Portion I. — Non-magnetic. 



This weighed 11-115 grams, and had a specific gravity, as a whole, of iVOlt. Guided by 

 the general appearance of the grains, a further sub-division of this portion of the material 

 was effected, the same becoming separated into three sub-portions a, b and c. 



Sub-portion a. — "Weighed 3'6*798 grams, and had a specific gravity of It'Sll. It was 

 composed of irregular-shaped grains and pellets, having comparatively smooth surfaces 

 and, so far as could be seen with the aid of a lens, quite free from any foreign inclusions. 

 A small proportion of the grains measured one millimetre, a somewhat greater nuinber 

 four millimetres, the greater number two millimetres in diameter. 



Sub-portion b. — Weighed 2"85*76 grams, and had a specific gravity of 1'7'562. It was 

 made up of very irregular-shaped grains, all of which were more or less pitted and 

 contained a little imbedded chromite. Very few of the same measured less than one 

 millimetre, the greater number were one millimetre, with here and there one measuring 

 three millimetres in diameter. 



Sub-portion c. — Weighed 4'5*776 grams, and had a specific gravity of 16' 126. The 

 grains and pellets constituting this material were also of very irregular shape, they were 

 all very much pitted, and contained inclusions of chromite; about one half of the same 

 measured three millimetres, and there was almost an equal number measuring four 

 millimetres, whilst two of the pellets measured five, and one, eight millimetres in 

 diameter. Analyses of these sub-portions gave the following results : — 



'Temperature, in all instances, 155° C. - 



