THE DISTRIBUTION OF GOLD IN DEPOSITS AND THE VALUE OF DIFFERENT STRATA.
No absolutely satisfactory explanation has yet been given of the distribution of gold in deposits. *
The
opinion is held by some that the precious metal is uniformly
disseminated throughout the beds. But this is the case only in very
exceptional instances, and the unequal distribution of the gold f is
so general as to have given rise in California to the expression " pay
dirt," which means the stratum or strata containing gold in amounts
which render work profitable.
Top Gravel sometimes pays.—In
a few instances the gold occurs in comparatively large amounts in thin
streaks of cemented gravel scattered here and there in the alluvions,
and in some shallow banks ++ it is quite generally disseminated.
Even in high banks the upper portion or " top gravel," when consisting
of fine light quartz-wash with no boulders or pipe-clay, and where the
cost of hydraulicking is very small (owing to the facilities of a heavy
grade, sufficient dump, and cheap water), lias been washed at a profit,
though carrying an insignificant amount of gold per cubic yard. For
this reason the miner always tests the whole of the deposit.
* See " The Auriferous Gravels of the Sierra Nevada of California," p. 516. By J. I>. Whitney.
+
On the subject of the relative position of gold in deposits see Report
of Mr. Stutchbury, Government Geologist of New South Wales; Quarterly Jour. Geol. Soc. 1858,
p. 583, M. A. Selwin ; " Gold-Fields and Mineral Districts of
Victoria," pp. 81, 82, 87, 131, 173, R. Brough Smythe; Cotta's " Lehre
v. d. Erzlagerstatten," vol. i. p. 101, and vol. ii. p. 556 ;
Murchison's 11 Russia
and the Ural Mts.," vol. i. pp. 482-487, and " Siluria," p. 456 ;
Whitney's " Auriferous Gravels of the Sierra Nevada." p. 361 ; J.
Grimm's " T.agerstStten d. Nutzbaren Mine-ralien," p. 26 ; Hartt's "
Geol. and Phys. Geog. of Brazil," pp. 50, 51, 159, 160 ; Mawe's
Travels, pp. 222-227 ; Munroe's " Mineral Wealth of Japan," Trans.
Amer. Inst, of Mining Engineers, vol. v. p. 236 ; " Gold Deposits of
Taragua," Ann. d. Mines, 1817, vol. ii. p. 202.
X See " Gold-Fields and Mineral Districts of Victoria," p. 84.
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