44 
Siberia and California is unequally rich; in the usual 
method of washing, however, there is always a great deal 
lost. Lately, a great part of the Californian gold has been 
obtained from the auriferous quartz, which is dug, and 
then crushed and washed by machinery, 
The following are the chemical relations of gold. It is 
not attacked by any single acid ; it is, however, easily solved 
by nitro-hydrochloric acid, and may be precipitated from the 
solution by the addition of copper or sulphate of iron. The 
solutions are used for galvanic gilding. Before the blow¬ 
pipe small granules may be melted without being changed ; 
if the gold contains silver, as it usually does, it imparts to the 
salt of phosphorus pearl an opalescent cloudiness on cooling. 
If the gold contains 80 per cent, of gold or upwards, the 
latter may be quite separated by boiling with nitric or sul¬ 
phuric acid; when it contains the silver in smaller quan¬ 
tities, the gold retains a part of the silver, so that it cannot 
be quite separated from it; such assays must therefore first 
be melted with a corresponding quantity of silver, in order 
to separate the latter from the gold, and the nitric acid must 
also be perfectly free from chlorine. Besides the gold 
which contains silver, there are also palladium, rhodium, 
bismuth, mercury, and tellurium golds, which must, how¬ 
ever, be considered as rarities. 
The principal telluric ores containing gold are the 
schrift-ertz, or graphic tellurium, and the white telluric ore. 
The schrift-ertz , or graphic tellurium , crystallises in 
small right rhombic prisms, which generally occur dissemi¬ 
nated and aggregated in small bundles and spear-like 
needles (Fig. 10 ). These bundles are of a light steel-grey, 
inclining to silver-white, of a brilliant metallic lustre and 
uneven fracture, sometimes with a variously-coloured tar¬ 
nish, of 1*5 to 2*0 hardness, so that it soils paper, and is of 
8*28 specific gravity. The composition is 60 of tellurium, 
30 of gold, and 10 of silver. Formula, Ag Te + 2 Au 
Te 3 , it is therefore a combination of 1 eq. simple tel- 
luret of silver with 2 of tri-telluret of gold. Before the 
blowpipe it melts readily, the tellurium volatilizing as 
telluric acid, and at last a grain of gold, containing silver, 
remains on the charcoal. It is found with foliated tellu¬ 
rium at Offenburg in tbe porphyritic clay. 
White telluric ore , which occurs in small rhombic 
prisms and netted crystalline-foliated aggregations, is 
almost silver-white, and contains, in addition to telluric 
silver and gold, a small amount of telluric lead and anti¬ 
mony. It is also preserved for silver and gold, and is found 
at Nagyag in Siebenburg. 
The native tellurium of Facebay also contains from 2 
to 82 per cent, of gold. The foliated tellurium, which 
crystallises in square tables, consists of telluret of lead and 
a small quantity of telluret of gold, with 9*0—9*11 of gold. 
It is of a lead-grey colour, and is also found at Nagyag. 
Fig. 11—13. Platinum. 
Platinum was first discovered by Ulloa, a Spaniard, in 
1735, in the river Pinto in Choco, near Popayan, and was 
called platinia, or silver-like gold, and was recognised by 
the Swedish chemist Scheffer, in 1752, as a new metal. It 
occurs native only in small, flat, roundish grains of metallic 
lustre (Fig. 11), especially in Brazil, from whence the 
specimens figured are derived; more rarely, it is found in 
larger pieces, with rough, uneven upper surfaces, or some¬ 
what worn by attrition on one side (Fig. 12) ; the hollows 
in it appear blackish-grey, from being covered with irite ; 
sometimes single cubic planes are seen, and small cubes are 
said to have been found at the Urals. Still more unfre- 
quently, it occurs in larger pieces of from 2 to 20 pounds, 
and even larger. Fig. 13 represents such a piece of 2 
pounds weight, which, like Fig. 12 , is also from the Urals, 
in the district of Nischni-Tagilsk, 15 miles north from 
Katherinenburg. In Columbia larger pieces, from a single 
ounce to a pound and a half, occur only rarely. 
Rough platinum has an iron-grey colour, inclining to 
silver-white, a moderate metallic lustre, a hardness of 5 — 6 , 
and a specific gravity of 17*5—18 ; before the plow-pipe it 
is infusible, and is soluble in nitro-hydrochloric acid; a 
residue, however, of osmium, iridium, rhodium, palladium, 
and ruthenium, is always left; it generally contains, in 
addition to these, a small amount of iron, which varies 
from 2 to 13 per cent. The solution is yellow, and is pre¬ 
cipitated by sal-ammoniac ; the deposit is a double chloride 
of ammonium and platinum, and when heated leaves the 
platinum in the form of a very fine powder, which exhibits 
a certain amount of cohesion, and is known as spongy 
platinum. This is by repeated heating, hammering, and 
pressing, brought into the desired forms, plates, wires, etc., 
and is used for the manufacture of various instruments 
and apparatus which of late have executed a powerful 
influence in physics and chemistry. Pure platinum has a 
specific gravity of 21*0—21*7, and the spongy platinum 
may weigh as much as 26*0. 
As to the mother-mineral of platinum we are not yet 
quite certain; that from Columbia appears to spring from 
the green-stone, that from the Urals from the serpentine; 
platinum has also been found in California, in the island 
of Borneo, and in the gold sands of Ava, as well as at St. 
Domingo, and in North Carolina. 
Platinum containing iron with 11—14*6 per cent, of 
iron, and iron containing platinum with 8*15 per cent, of 
platinum, is found in the gold sands of Kuschwa. Pla¬ 
tinum-iridium, with 55*44 of platinum and 27*99 of iridium, 
containing a small quantity of rhodium, copper, iron, and 
palladium, of 16*94 specific gravity, has been found in the 
platinum-sand of Brazil. The value of rough platinum is 
three or four times that of silver, of pure and manufactured 
platinum, about eight times. 
Platinum has been long applied to the coinage and to 
medals in Russia; this use of it has, however, been discon¬ 
tinued. At present it is only used for wires, plates, cru¬ 
cibles, cups, distillation vessels, and galvanic apparatus; 
it is, however, indispensible for many purposes, in which 
its infusibility, combined with its great ductility and dura¬ 
bility, as well as its indifferent relation to simple acids, are 
of remarkable value. Spongy platinum is used for pro¬ 
ducing lights, and, on account of its catalytic properties, 
for bringing about chemical combinations and the like. 
Iridium. 
One of the many metals which usually occur with pla¬ 
tinum, and frequently render it impure. It was discovered 
in 1803 by Tennant. 
Native iridium is found in silver-white grains, which 
