portions
of the native rock arc attached, so that by carefully marking these
indications, the shrewd observer is able ta form a good guess of the
vicinity of mines which will amply repay the acuteness of his
observations.
Our
space will not allow us further to enter into geological
considerations, and we will now give the reader a few mineralogical
characteristics of gold, so that he may know it when he finds it, this
not being so easy a matter as he may imagine. False alarms without end
are of constant occurrence in all the Australian colonies, the
discoveries turning out neither more nor less than pyrites of some kind.
Gold
is yellow, nearly silver-while, and steel-gray; the yellow is the most
common in Australia. Its lustre is shining which is increased by a
little rubbing, when it will not again tarnish from its non-oxidable
qualities. In colour and lustre it may easily be mistaken for iron or
copper pyrites. A cut with a knife or a blow with the hammer will at
once rectify this mistake as it is soft, whilst iron pyrites is harder
than steel, and if struck it flattens, whilst copper pyrites is not
malleable, but crumbles before the blow. Mica is again often mistaken
for gold, but the weight of the latter will at once point out the
mistake, as mica is light. The steel-gray gold may be mistaken for
platinum, but as it is rarely found in this condition in Australia, the
difference is unimportant, and can only be detected by experience or
assaying. The softness and the weight are the best tests. Is is softer
than iron, copper or silver, and harder than tin and lead. Hence it is
scratched by the three former metals, but scratches the two latter.
When
broken, the edges arc uneven. It is sometimes found in a crystalline
form, and when so, its value is much increased, as being a rare
mineralogical specimen. Sometimes it occurs in thin leaves. Should all
the above indications not prove satisfactory, the blow-pipe, with which
every emigrant should provide himself, is a sure lest. Before this it
fuses readily, and remains unaltered, whilst copper and iron pyrites
have a sulphurous smell and rapidly diminish.
A
bottle of nitric acid is sure test. If the mineral found be gold, it
will not touch it; if a baser metal, with the exception of one or two
not commonly found in Australia, violent action takes place and
gaseous fumes arise. By Ihis means spurious gold dust may be delected :
if it be pure, no action whatever will take place, and the liquor will
not be discolored ; if impure, violent action -will lake place, red
vapour will arise, and the acid will be discoloured.
The
weight of a lump of quartz as estimated by poising it in the hand is
generally sufficient to determine whether it contains gold or not,
quart/, having a specific gravity of about 2.1, whilst the specific
gravity of gold is from 18 lo ly. This accounts for gold being sound in
grains and nuggets—the water having had sufficient power lo break up
and wash away the lighter rock, but not Ihe gold itself. Hence it may
be inferred that when large lumps of gold are found, Ihe matrix itself
cannot be far off—from ihe impossibility of Ihe current washing these
to any great distance. On the other hand if the gold be in dust or
scales, it may be, and is frequently distributed over a large space of
ground.
The
unpractised miner is apt to take several substances for gold which have
no alliance with that metal. The first of these is yellow mica: this
may, however, be readily distinguished by its lightness. The next is
iron pyrites. This is as easily distinguished. Stick the point of a
penknife into a scale of gold, and it will penetrate it, but the
pyrites would be found too hard for this. Place a little of the
substance on a shovel, and put it on the fire. If it be pyrites, a
strong smell of sulphur will be perceived, and the residuum after the
sulphur is driven off will become red iron rust. Dissolve the mineral
in muriatic acid, and add a few drops of nitric acid. Add to the
solution a little bartshorn, and, if iron pyrites, rust is
precipitated, With a solution of
