Tracking (Tracing) Float (Part 2)
I'm feeling a bit under the weather with one of the various "cruds" going around, so I may not be at my top form in this post but I'll still give it my best shot. That said, let's move on to more about tracking float (gold ore).
You'll note I use the term "tracking" while the more common term (and the one the old timers used) for following float is "tracing." It's six of one and a half-dozen of the other really. I like using tracking since following gold ore to its source reminds me a lot of hunting or tracking animals. My pard "Muskrat" at Muskrat Outdoors knows a lot more about this sort of thing than I since he hunts and traps for food and to supplement his income. Anyway, in order to track, hunt, or trap animals you must have very good knowledge of their behavior in all aspects and the locations they can be expected to be in. Tracking float has many similarities to this idea of hunting or trapping, and if you aren't very well versed in tracking animals you probably aren't going to do very well at it. Ditto for tracking loose gold ore or float. That's why I'm always harping about getting some gold ore identification and gold ore geology knowledge under your belt. Again and again I've said this and I'll say it again here: "Knowledge is power." I've probably not stated this hunting and trapping analogy very well, but I trust you understand what I'm trying to say.
The old timers went about tracking float in a number of ways, including trenching and boring. I won't be talking about these subsurface methods of tracking float since they aren't usually the province of those of us who are placer miners. However, they are proven standards for those committed to finding and developing hard rock or lode mines. So it's apples and oranges to a great degree here. But if one of you were to track some decent float to a long-forgotten or bypassed ore body, knowing something about these subsurface methods may come in handy and you can always hit me up about what these methods entail. But know this first and foremost: I am NOT a hard-rock miner or prospector. The bulk of my field experience has been as a placer miner, just like many of you. Like I told reader Doug B. a while back, I know just enough about lode mining to be a danger to myself and others! So I don't claim to be an expert in locating, developing, or mining hard-rock ventures. But I do know something about the subject of this post series...tracking float. And in this series we'll be talking solely about tracking float using surface techniques and methods.
Here, for your consideration, is my version of tracking float based on what the old timers knew and did back in the 1800s and early 1900s:
1) You have to be in an area where gold mineralization or the presence of gold is known or anticipated. So the upshot here is that you won't find gold float in areas where it doesn't exist or can't exist, geologically speaking. As I've said before, despite their lack of formal knowledge about gold ores, the old timers had a practiced eye when it came to spotting anomalies out in the field. More often than not, they had already found placer "showings" of color in washes, gullies, or streambeds or had picked up and scrutinized suspected gold ore up on terraces or hillsides before they began their float search for potential sources.
2) There has to be the presence of the disintegration or eroding out of vein material on the surface. Subsurface lodes or vein material aren't going to do you much good in tracking float for obvious reasons. There has to be surface erosion of exposed vein material in your area. This float will, like most rock, tumble ever downward from its source as time passes and natural forces like snow, wind, rain, and good old gravity do their thing. In some desert locations, however, exposed lode veins or blow outs have occurred in spots in low-lying areas some distance away from hillsides and the resultant float spread far and wide over the desert floor. How this "spread" on nearly flat ground occurs is open for debate, but Ma Nature is pretty powerful when it comes to her natural forces.
(Image courtesy of the Mining Alliance.)
3) The smaller the pieces of float the farther away the source. This is a generalization of sorts but it holds true for the most part and it's something the old timers knew quite well. There is a good analogy here with placer mining that most of you know very well too. Again in general, the smaller the pieces of placer gold and their relative smoothness, the farther that gold has traveled. The coarser that placer and the larger its size, the less distance it has traveled. Most importantly, any placer that has matrix material still bonded to it indicates a source that's fairly close by. For the old timer hard-rock prospectors this held true as well as they sampled streams or washes, or came across float. The larger the pieces or chunks of float and the more visible gold it contained, the closer they were to the source. Additionally, when you first start tracking float there may only be a single piece here and there to follow. If you're following things up properly, those pieces of float will start to increase in number (and yes, size).
4) Not all float is going to display visible gold. But the old timers had a very keen eye for gold mineralization in all its forms and if they found and tracked float they found worthy of their attention, they carried samples to the nearest assay office to find out exactly what they were dealing with. Although most of the gold ores the old timers dealt with were quartzitic or pyritic (i.e., gold in quartz or ore showing heavy iron sulfidation and gold), sometimes their eyes were caught by float that showed little in the way of visible gold or iron pyrites. Some of these "mystery" ores were refractory, or ores where the gold constituency within them was in a chemical form that could only be recovered through a complex process. Again, if you're interested in tracking float and know little about gold geology or haven't been out in the field much, you're gonna have a very hard time of things brothers and sisters.
(Is there still float like this around? Yes, somewhere out there...)
5) Not all float is worth tracking. This is an adjunct of the previous point. Float is, for our purposes, material that has eroded out of vein material, lodes, blow outs, etc. Not every piece of float is gold bearing. In fact the reverse is true in most instances. This is due to the fact that not every inch of a lode contains matrix material with gold in it. I've seen goodly amounts of float scattered across large alluvial fans in desert gold areas that was mostly just pretty rock without any gold in it. So at some point you have to make a decision as to whether following a particular float is worth the effort. Now the old timers (the really adept ones with a nose for gold, that is) were not always put off by this issue. They often forged on ahead if they thought the visual clues or "signs" were intriguing, but they never kept on tracking "bull quartz" or what they called "dead" rock (rock that showed no sign of gold mineralization).
(Looks like bull quartz to me, but there is some iron oxidation.)
6) Float can be close by or far away. Despite the presence of placer gold in a stream or wash, the source or sources of that gold can be farther away than you may think. This was something the old timers learned through experience and there are no fixed rules to go by when considering it. I guess the reason I'm throwing this out there is to deflect the idea that float is always close by. Sometimes it is and sometimes it isn't. Again, float's size is often the predictor of how far away it is from the point you decide to track it to its source. Some old timers were fooled this way when their sampling or panning of alluvial or elluvial gold stopped showing color. Many assumed that the gold ore whose source they were seeking lay close by but were brought up short when they moved hundreds of feet (as much as 400-500 feet in certain old timer diary entries) before finding their first piece of true float.
I hope all this isn't to scattered or confusing for you. Again, my brain is not working at its highest capacity today nor is it as sharp as it should be. Anyway, we'll talk more about tracking float next time.
Take care all.
(c) Jim Rocha 2019
Questions? E-mail me at email@example.com