460 



METALS. 



Lunenburg, though gold occurs in the quartz 

 veins, most of the product has been ob- 

 tained from the sand of the beach, and a 

 " dredging company " has been formed to ex- 

 plore the bottom of the harbor. Mr. Marsh's 

 analysis of a specimen of gold from Tangier 

 shows it to be of amost unequalled purity, con- 

 taining 98-13 per cent, of gold, 1'76 silver, 0-05 

 copper, and a trace of iron. It seems impos- 

 sible to ascertain how much gold has been ob- 

 tained up to the present time in this region, as 

 the miners were generally unwilling to give 

 such information. 2,400 dollars were said to 

 have been taken from one claim at Tangier, 

 $1,300 from another, and $480 from a third, and 

 at Lunenburg $250 were taken from a single 

 pocket. At Sable Island, which is more than a 

 hundred miles from the coast, a small quantity 

 of gold has been found in the sand, appearing to 

 indicate that the gold-bearing strata extend for 

 a considerable distance beneath the Atlantic. 



Researches on the Platinum Metals. In the 

 " American Journal of Science," Jan. 1861, is a 

 portion of a valuable paper on these metals, by 

 Dr. Wolcott Gibbs, who has for several years 

 devoted much time to their investigation. The 

 material used was obtained chiefly from the New 

 York Assay Office and the Mint, and included 

 also a considerable quantity of Siberian osmi- 

 ridium. The samples obtained from the Mint 

 at various times, and which had been subjected 

 to different preliminary processes, varied great- 

 ly in appearance. In some cases the ore was 

 in distinct scales, rather whiter than the Sibe- 

 rian osmiridium ; in a sample of this kind Dr. 

 Genth detected distinct crystals, belonging to 

 the rhombohedral system. Other specimens 

 resembled a fine gray metallic sand, while 

 others again (derived from the sweepings of 

 the Assay Office) presented a heavy gray pow- 

 der. Nearly all the ores contained more or less 

 iron mechanically mixed, which could be ex- 

 tracted by the magnet, or dissolved out by 

 acids. Nitre-muriatic acid acted powerfully 

 upon many specimens, dissolving portions of 

 the platinum rnetals as well as iron, and even so 

 far attacking the osmiridium itself as to occa- 

 sion a distinct evolution of free osmic acid. In 

 California the ore is almost always associated 

 with gold, from which it is of course impossible 

 to separate it by washing. At the Assay Office 

 the gold is melted with twice its weight of sil- 

 ver, and the osmiridium allowed to settle. 

 When the gold alloy is poured off, there remains 

 a mass containing nearly all the osmiridium 

 mixed with gold. This mass is fused repeated- 

 ly with silver, and the last traces of silver and 

 gold are finally removed by treatment with 

 nitric and nitro-muriatic acid and washing. 

 The osmiridium is sold to the manufacturers of 

 gold pens, who extract from it the excessively 

 hard particles which serve for the points of 

 pens ; the rest is returned to the Assay Office. 

 The amount of osmiridium obtained in this 

 way does not exceed a few ounces in many 

 millions of dollars, and many samples of gold 



are entirely free from it. It cannot, however, 

 be doubted that large quantities of the ore will 

 be obtained whenever important practical ap- 

 plications of the metals contained in it shall 

 create a demand. The density of different 

 Californian samples varied very much ; one 

 specimen, in large dull white plates, but slight- 

 ly acted on by nitro-muriatic acid, having a 

 specific gravity = 19'352. It is probable that 

 this arises from differences of composition in 

 the separate scales. G. Rose gives the density 

 of the Siberian ore at 19'3 to 21*1. Dr. Torrey 

 has found among the Californian scales some 

 which could be flattened under the hammer, 

 and were probably platin-iridium. In general, 

 however, the scales are not malleable ; some 

 of a lead-gray or bluish tint being with great 

 difficulty cut by the emery dust employed 

 by the gold pen-makers. In color the scales 

 vary from nearly silver- white to dark gray. To 

 this part of the paper Dr. Torrey has added the 

 following notes on the Californian osmiridium : 

 " For the first year or two after the establish- 

 ment of the United States Assay Office, the 

 proportion of osmiridium in the California gold 

 did not exceed half an ounce to the million of 

 dollars. Afterwards, the proportion rapidly in- 

 creased till the average was seven or eight 

 ounces to the million of gold. Then, for a year 

 or more, the quantity diminished, but for the 

 last year it has been as large as ever. These 

 differences depend upon the variable composi- 

 tion of the native gold, and the constant dis- 

 covery of new diggings. The grains of osmiri- 

 dium, suitable for pens, are roundish and solid, 

 not liable to exfoliate when struck or heated. 

 They seem to have a different composition from 

 the compressed and tabular crystals. The pro- 

 portion of them is usually not more than a tenth 

 of all the alloy, but it is sometimes as large as 

 one-fifth. The carefully-selected grains used 

 by the gold pen-makers are so minute that from 

 10,000 to 15,000 of them are contained in a sin- 

 gle ounce. The very best are worth at least 

 $250 an ounce, and a cubic inch, which would 

 be equal to about eleven ounces, is worth 

 $2,750." The purely chemical part of the pa- 

 per, though of the highest interest, hardly ad- 

 mits of condensation, as its value mainly con- 

 sists in its minute details of necessary precau- 

 tions to be observed in the treatment of the 

 ore. The process recommended is essentially 

 that of Glaus, with some modifications rendered 

 necessary by the peculiar composition of the 

 Californian ore, which, according to Dr. Gibbs, 

 contains more ruthenium than the Siberian. 



Dimorphism of Arsenic, Antimony, and Zinc. 

 In the " American Journal of Science," for 

 March, 1861, Prof. J. P. Cooke, of Cambridge, 

 describes a series of experiments tending to 

 prove that, besides the rhombohedral forms of 

 crystallization of these metals, they are also 

 capable of crystallizing in regular octahedral 

 and other forms belonging to the cubic system. 

 Arsenic was stated by Eisner, in 1841, to have 

 been obtained in octahedra, by subliming a 



