(Oh that yellow metal...)
Gotta love those heavies, especially gold. The magical luster of that yellow metal has enthralled me since the first time I saw a crescent of it show up in a gold pan. The other heavies associated with gold may not be as pretty or as valuable, but they can be important signposts to where the good stuff is resting.
Bet on the Fact...
You know, stream and wash hydrology is as interesting as it is complex. Any small-scale gold miner without a decent measure of understanding concerning hydrological factors is likely to come up short when it comes to getting the gold (not to mention pissing into the wind from an overall mining standpoint). Maybe that's one reason I harp about it so much. Anyhoo, you'd be well-advised to listen to my questionable diatribes just the same. I actually DO know what I'm talking about...at least most of the time.
Hundreds of Data Points
What's normal water flow? That ideal "in between" distinguished by flooding on one hand and low water conditions on the other. Try to imagine that river, creek, or stream's hydrological status being displayed on a 12-point colored scale (like a thermometer's) with the numbers 9-12 at the bottom and the area they are in colored white (low). The numbers 5-8 are in the middle of the scale, which is painted blue (normal). Finally, at the top we have a red area (flood, flash flood) that encompasses the numbers 1-4. In Ma Nature's realm, this primitive color scale for water flow would be much more complex with literally hundreds and hundreds of data points that coincided with the slightest variations in stream hydrology. But I'm essentially a simple guy (simpleton??) so let's keep things going with my basic 12-point scale. And let's take things a step further by relegating that scale to wet placers only, since dry placer hydrology is a different beast altogether.
(Want data points? There are plenty out there.)
Heavies are probably not going anywhere at all if our hydrological scale is in the white, especially as we approach the number 12 at the bottom of that scale. There's simply not enough force in white-scale conditions to move heavies around or even roust them from their usual hiding places. Even in areas with eddy currents or small suction vortices this will hold true, although occasional bits of fine gold, an occasional garnet, or very small, thin flakes might wash down from upstream. But the heavies? They are going nowhere. Like they say, however, "Every dark cloud has a silver lining." Not much new gold or other heavies will be deposited during low-water conditions but to balance things out accessing the existing gold will be made much easier, relatively speaking that is. This has been proven out over the past few years in the California Motherlode Region where extensive drought conditions have left most of the area's gold-bearing streams highly vulnerable to crevicers, gold snipers, and even casual gold panners.
(Low water conditions may not move heavies, but they certainly provide access to them.)
Moderate, stable water flow (blue scale color) will mix and move lighter materials around, including flakes and fines that have entered the stream flow. Ditto for smaller garnets, some oxidized iron materials, and perhaps the smallest pieces of lead or fractions thereof. In truth, the deposition of gold and other heavies in moderate water flow is not great, but it does continue and has a lot to do with the actual hydraulics in any given section of a gold-bearing stream. Some streams move more rapidly than others or are configured in such a way as to either hinder deposition or greatly enhance it. The variables are the key here, but they can be bewildering because they are so numerous and so complex. In moderate flow conditions, most "heavy" heavies will remain in place where they dropped out into the stream in the first place.
(Although not earth shattering in nature, there's some heavy movement and deposition under moderate flow conditions.)
Where do the heavies drop out? And what about red-scale water flow conditions? Stay tuned for the next post and I'll tell you...
(c) Jim Rocha (J.R.) 2016
Questions? E-mail me at firstname.lastname@example.org