Gold '^Pockcf Deposits in Northern California. — Hcrshcy. 41 
be the correct theor)- of the mode of their formation. No miner 
has ever advanced it, and, so far as I know, I have an exclusive 
monopoly of its present conception. The very unusual nature 
of it will give it more than mere local interest. 
After the Carboniferous period, the site of Trinity county 
was a land area for a sufficiently long time to cause a profound 
denudation of the three ancient rock systems of that area — 
the serpentine and white quartzyte formation, the schist forma- 
tion, and the schistose clay slate formation — and then great 
fissures were opened somewhere and melted lava flowed out 
upon the land surface, overspreading a broad area in a thick 
sheet, and solidifying to form the most interesting formation 
of the entire country, the green diabase. Gold, probably in 
chemical combination with other elements, was an original 
constituent of this sheet of diabase, and to-day, according to a 
prominent assayer of Redding, Cal., occurs universally dis- 
seminated through it, (largely in combinationwith chlorine), 
not infrequently portions of the diabase assaying at the rate of 
$2.00 to $3.00 per ton of rock. That this great green massif is 
the source of practically all the gold in the black slate area of 
eastern Trinity county and western Shasta county, I have 
gathered, during practical prospecting work, overwhelming 
evidence of, which I cannot detail here. 
Half a dozen distinct vein systems cut the diabase, yet only 
one contains gold in a concentrated condition. This is why the 
greater portion of the area of the diabase country is barren of 
paying mines. A certain particular set of conditions had to be 
fulfilled to gather the disseminated gold and concentrate it into 
the quartz veins. Some of these rich veins are lens-shaped, 
being completely surrounded by solid, unfissured country- 
rock. Indeed, small nuggets of gold have been found in the 
amygdaloids of the upper portion of the formation. In these 
cases, no idea can be entertained that the gold came from a 
great depth. It was taken into solution in neighboring por- 
tions of the diabase, by water slowly moving through the 
minute pores, and deposited along with the quartz in the 
amygdaloid cavities. 
The surface of the diabase was subjected for a considerable 
])eriod to subaerial denudation. The decay of the rock freed 
the gold which, being heavy and practically indestructible, re- 
