(Plant life can provide important visual prospecting clues.)
First things first...Happy New Year to one and all. In this post I'll be talking primarily to you hard rock gold prospectors out there, although you placer miners should take heed because the information in this post should prove valuable to you as well.
In the past, I've talked a little bit about visual clues that can lead you to gold-bearing zones and their coincidental outcrops, veins, and stringers. This latter term may not be familiar to all of you, so let me explain. Stringers are small (in width and typically length) gold-bearing veinlets that can be found in mineralized host rock. Undoubtedly, many of you have come across rock faces that were literally shot through with quartz stringers. Most of the time these stringers are composed of what the old timers called "bull quartz." Whether the old timers used this term facetiously as a correlate to the term BS, I don't really know but it's highly likely knowing their penchant for sardonic humor! At any rate, "bull quartz" is sterile and typically contains no gold whatsoever. You can bang away at it all day long with hammer, chisel, and rock crusher but your efforts to find a trace of color in it are probably going to be futile.
(Quartz stringers in host rock...looks like "bull" to me!)
That definition established, let me move on. As you well know, the old time hard-rock gold prospectors were not highly educated men or women in the formal schooling sense. With time and experience in the field they became very adept at spotting potential gold-mineralized zones and locations, however. Some (notice I said "some") of the visual clues they looked for were:
1) Contact zones (areas where two diverse geological types met, or "contacted" one another).
2) Coloration (veins, rocks, or "float" showing signs of sulfides or other chemical constituents where yellows, reds, rusty oranges, blues, greens, greys, blue-greys, blue-greens, etc. were predominate or mixed together).
3) Float (smaller rock that eroded out of host vein material or rock faces exhibiting a variance from the prevalent host or country rock and showing coloration, the presence of iron sulfides like pyrite, or visible, free-milling gold).
(Notice the free-milling gold in this sulfide type ore.)
4) Placer gold (alluvial gold found in low-laying areas such as gullies, washes, streams, or elluvial gold on benches or slopes indicating erosion from a nearby source).
5) Alterations in local plant life (stunted, contorted, withered, coloration changes, excessive growth or gigantism, or the sudden disappearance of plant life as a whole).
The plant life factor here is more important than you might think and seems to cause the most confusion among my readers and among hard rock prospectors themselves for any number of reasons. So let me explain. Most gold-mineralized zones contain a range of chemical constituents that can cause either benign (additional growth or gigantism) or malignant (stunting, withering, color changes, disappearance, etc.) changes to local plant life, including trees in some instances.
Typically, however, chemically based hard-rock gold zones don't do plants a whole lot of good. This is especially true if there's a natural leaching effect from erosion in the area. Consider the adverse impact of mercury, sulfides, lead, or other potentially harmful solids or solutions on the human body and you get an idea of the issue at stake here. Often, these chemically charged rocks or veins lie directly beneath an area's plant life which should give you would-be prospector's out there cause for thought concerning what might lie right underneath your boots. This is by no means a scientific explanation of the plant-life aspect of visual prospecting clues, but it may help some. Another thing to remember here is that the visual clues associated with plant life can also be (and often are) simply the result of changes in altitude, rainfall rates (or lack thereof), heat or cold, or any number of other natural forces. This is the literal monkey wrench in the works, isn't it?
Interested in Furthering Your Knowledge?
This whole plant life thing is a visual prospecting clue that most gold prospectors and miners know little, if anything about. When it comes to finding gold, any lack of knowledge on your part is detrimental so I suggest you school yourself up a bit on this least-known aspect of visual prospecting. To that end, let me recommend a book on the subject to you, OK? The book in question was published in 1983 and to my knowledge is the ONLY scientific treatise on the subject out there. So if you're interested in furthering your knowledge, purchase Biological Methods of Prospecting for Minerals by R. R. Brooks. Be prepared to pay a premium for this book because the last time I saw it for sale online the price tag was $56.00 USD for a USED copy! But hey...if the book helps you find gold it'll pay for itself, right?
(This copy of Brooks' book is for sale on eBay.)
It goes without saying that dry or desert areas probably provide the optimum grounds for visually oriented gold prospectors which is why so many rich hard-rock gold strikes were made in the desert regions of California, Arizona, Nevada, New Mexico, and countless other similar regions throughout the world. There's a simple reason for this fact. Dry or desert areas usually contain sparse plant life which makes it easier to spot plant-life anomalies and to eyeball surrounding terrain. In deserts, visual clues jump right out at you, while in heavily forested and plant friendly areas like California's Motherlode Region you can play literal hell just trying to spot the local country rock let alone a vein outcrop.
My take on small-scale gold prospecting and mining has always been keep on learning. Just because you've been around the mining block for a decade or two doesn't mean you know everything and can now plop your lazy butt down to rest on your laurels (I'm speaking figuratively here!). You want to know something brothers and sisters? Yours truly has been at this gold mining and prospecting thing for over three and a half decades now and I'm still learning, so why can't you? Like they say, "Knowledge is power." I'll take that a step further by saying that a well-informed and educated prospector or miner has a leg up on the competition. Want to find more gold? Leaarn as much as you can and never stop that process.
Best of luck out there!
(c) Jim Rocha (J.R.) 2014
Questions? E-mail me at email@example.com