NOTE ON THE ORIGIN OF MALACHITE. 
(Observations made in an abandoned Copper Mine.) 
By Epear Hatt. 
(Communicated by Prof. LiversipG£, M.A., F.R.8., &c,) 
[Read before the Royal Society of N. S. Wales, December 4, 1895.] 
Ir is now generally conceded by mineralogists that the oxidised 
portions of mineral lodes represent merely the weathered condition 
of the originals, and that the oxide, carbonate and sulphate 
minerals contained therein have been formed by atmospheric 
influences alone. Very few men of experience in the every day 
working of mines now think those influences to have been abnormal 
at any time. All the phenomena can be explained by the changes 
which are still going on, and present atmospheric conditions are 
ample to produce the weathering seen at the largest of mines. 
Such being the case, abandoned mines offer an interesting field of 
study to a mineralogist, as their workings expose large surfaces 
to the action of air and water. 
Numerous as are the abandoned mines of New South Wales, 
the number available for examination and likely to yield valuable 
information, is small. This is due to two reasons; one is, that 
the mines have not been abandoned long enough, and the other, 
that most of the mines are situated in the eastern coast ranges 
where the rainfall is high, and consequently the mines get filled 
with water to a point very near the surface. It is obvious that 
8 comparatively arid climate, or one where long periods of dry 
weather alternate with intervals of heavy rainfall, is required to 
produce large masses of oxidised ore bodies. Such a climate 
obtains in our far western districts, and accounts for the largé 
bodies of oxidised ores found at Broken Hill, Cobar, and other 
well known places. 
In such a climate oxidation proceeds very rapidly. Iron py rites 
where occurring in large quantity will, in four or five years, al 
