What good would it do even if that clipping is true ? And what good would it do if you found the exact spot ?
In the 139 yrs. since that clipping date, the entire state has been mapped out for soil types, prospect potentials, mineral surveys, etc..... I mean, in general as per vicinity, ranges, etc.... So to whatever extent those low-lying hills east of Oakland have any mining potential, that is long since assayed/surveyed out. There's not an area of CA that you can't already avail yourself of the govt. surveys, that were done/mapped ages ago.
And sure, gold got discovered at lots of hills besides the more optimum Sierra nevada motherlode. Heck, there's even gold in the sands along the seashore at certain river outlets, where folks have gotten varying amounts by simply running it through mercury (d/t it came down geologically/historically in the waters, and is now in the black-sands along the beach.) But by no means in any sort of commercially viable form to extract.
Same for the low lying hills around Santa Cruz, and south of Monterey (Los Burros, etc...). Gold was found there too. But it was not viable for commercial ventures, hence the eventual failures of such efforts.
So too is something in the hills east of Oakland gonna be: So what ? And as for anything habitation related (ie.: the miner's house, cabin, or whatever, if relics/coins were what you had in mind), I also say: "so what?". There is SCORES of locations around Oakland, Alameda, Berkeley, SF, etc... where you can avail yourself of terra firma that had people-traffic as far back as 1876. And no doubt homestead (or even, gasp, mine attempts) back in the hills there. And you can already detect there and hope for a coin or relic of that era. Urban demolition in Oakland will often reveal those stratas, capped from modern garbage intrustion, since they've been covered with a building, or street, or sidewalk etc.... for the last 100+ yrs.
Thus I'm not too sure why md'rs eyes "wax romantic" at the thought of "lost mines" all the time.