PLACER GOLD OF THE BARKERVILLE AREA. 549

fillings and the linear ridges represent veinlets of gold deposited
in subsidiary cracks in the walls of fissures.

In many specimens the rugged protuberances on the more angu-
lar pieces of placer gold may be seen slightly rounded and bent
over, just as one would expect them to be shaped in the transition
from vein gold to placer gold. Many of the curved protuberances
enclose, in the concavity beneath them, angular fragments of
quartz, which had not been separated from the gold by abrasion.
When the bending of these salient parts of the angular gold has
proceeded to a more advanced stage, the quartz grains become
entirely embedded in the nugget. The mammillary character of
the surface of many of the nuggets is probably explained by such a
process.

One slightly worn piece of angular gold shows on both sides a
number of triangular depressions shaped like the corner of a cube,
from which crystals of pyrite have no doubt been removed.

Many specimens of galena, found in the placer deposits, show
small amounts of free gold. Close inspection of several such
specimens and of polished surfaces of them revealed the fact that
the gold occurs in veinlets or in well-developed cleavage cracks in
the galena or in reéntrant portions of the specimens. One speci-
men, consisting of brownish sericite schist from the country rock
of the region, showed veinlets of gold traversing the rock, both
parallel and transverse to the schistosity.

Polished and etched nuggets (Figs. 73 and 74) from the dis-
trict show several features, which throw some light on the origin

of the placer gold. Nugget No. 1 (Fig 73) shows crystal faces
but is somewhat worn; the other nuggets are well worn. The
nuggets when polished and etched show a definite crystalline struc-
ture and it is probable, as has been found in other regions,® that
nearly all the placer gold as well as the vein gold is crystalline,
and only a small part concretionary. Nugget No. 1 is composite
and consists of a large crystal occupying the middle part with
additional crystal growths at both ends. All the nuggets show

* Liversidge, A., Jour. Roy. Soc. N. S. W., XXVIII., 1893, p. 343; ibid., XXXI.,
1897, p. 79; ibid., XL., 1906, p. 161.