Eldorado Creek, the most important tributary of Bonanza Creek, is a small stream about seven miles in length and from three to six feet in width at its mouth. The Eldorado Creek gravels are precisely similar to those on Bonanza Creek. They consist of from five to nine feet of flat, schistose and angular or rounded quartz pebbles, covering the bottom of the valley in a fairly uniform sheet, overlain by a few feet of frozen muck.
Considerable areas of quartz-drift occur at the mouth of Eldorado Creek, forming part of the Gold Hill deposit, and on French Hill immediately below French Gulch, while smaller patches occur about half a mile below French Gulch on the same side, and half a mile below Gay Gulch on the right limit.
The productive portion of Eldorado Creek extends from the mouth of the valley up to near Gay Gulch, a distance of about three and a half miles. The gravels along this stretch of the valley were of extraordinary richness, and few breaks have been found in the continuity of the pay-streak. Some of the claims yielded more than a million dollars each, or at the rate of $2,000 per running foot, while ground running $1,000 per running foot was common. The pay-gravels extended, with varying values, all across the bottom of the valley, and had a thickness of from three to four feet. The gold also penetrates the bed-rock to a depth of two feet or more. The upper part of Eldorado Creek was not as productive.
Eldorado gold is very coarse and is often almost unworn. Nuggets are more plentiful than on the other creeks, and are often found in an imperfectly crystalline condition. The gold is lighter in colour and of a somewhat lower grade than that of Bonanza Creek.