re
liberated.

Many colloidal solutions of copper have been obtained. A reddish-brown
solution is obtained from solutions of copper chloride, stannous
chloride and an alkaline tartrate (Lottermoser, _Anorganische Colloide_,
1901).

_Occurrence._--Copper is widely distributed in nature, occurring in most
soils, ferruginous mineral waters, and ores. It has been discovered in
seaweed; in the blood of certain Cephalopoda and Ascidia as haemocyanin,
a substance resembling the ferruginous haemoglobin, and of a species of
_Limulus_; in straw, hay, eggs, cheese, meat, and other food-stuffs; in
the liver and kidneys, and, in traces, in the blood of man and other
animals (as an entirely adventitious constituent, however); it has also
been shown by A. H. Church to exist to the extent of 5.9% in turacin,
the colouring-matter of the wing-feathers of the Turaco.

Native copper, sometimes termed by miners malleable or virgin copper,
occurs as a mineral having all the properties of the smelted metal. It
crystallizes in the cubic system, but the crystals are often flattened,
elongated, rounded or otherwise distorted. Twins are common. Usually the
metal is arborescent, dendritic, filiform, moss-like or laminar. Native
copper is found in most copper-mines, usually in the upper workings,
where the deposit has been exposed to atmospheric influences. The metal
seems to have been reduced from solutions of its salts, and deposits may
be formed around mine-timber or on iron objects. It often fills cracks
and fissures in the rock. It is not infrequently found in serpentine,
and in basic eruptive rocks, where it occurs as veins and in amygdales.
The largest known deposits are those in the Lake Superior region, near
Keweenaw Point, Michigan, where masses upwards of 400 tons in weight
have been discovered. The metal was formerly worked by the Indians for
implements and ornaments. It occurs in a series of amygdaloidal
dolerites or diabases, and in the associated sandstones and
conglomerates. Native silver occurs with the copper, in some cases
embedded in it, like crystals in a porphyry. The copper is also
accompanied by epidote, calcite, prehnite, analcite and other zeolitic
minerals. Pseudomorphs after calcite are known; and it is notable that
native copper occurs pseudomorphous after aragonite at Corocoro, in
Bolivia, where the copper is disseminated through sandstone.

_Ores._--The principal ores of copper are the oxides cuprite and
melaconi