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Saturday, November 19 2022

If you’re used to water mining, having success in the desert might seem challenging— that is until you start thinking of desert ground as a massive sluice box. Many of the principles you’re used to when prospecting and mining in waterways, will translate into desert mining. The most important thing to remember is that water is crucial to gold movement. Unlike a running river or creek with highs and lows, desert placers are much different in that gold is moved quickly during a flash flood, leaving gold stranded as opposed to being moved further by continual water flow in a creek.

During a river high-water event in a non-arid area, gold is moved over a larger area by massive water flows that continue until the water slows as the source dissipates its energy. Spring snow runoff is a good example. Rivers rise and sometimes flood based on the upstream water source. When the snow has melted, the river will slowly get back to  normal. In the desert, gold is moved in the exact same way with the exception that water powerful enough to move gold does so and then just simply stops. In a flash flood, gold is moved very violently and often a very short distance, sometimes percolating into valuable pockets. Here’s where the difference between water and desert mining principles comes into play generally flood gold will concentrate in areas that do not meet the standard thought of inside bends and where the water flow becomes lower.

For the most part, desert mining experts recommend staying out of the washes, gulches and dry river beds— that is unless you clearly see exposed bedrock. Gold will settle fairly quickly when it is trapped behind jagged bedrock and small fault lifts that have not been worn down over time by constant water flow. It IS true you can find areas of concentrated gold-bearing material in the washes, however, the amount of time and energy to get through feet of overburden is usually just not worth it, especially when there are higher values to be found outside of the wash.

Follow the leads out of the wash to where the gold lives in higher concentration. Test and sample areas you see with a great deal of runoff from a tributary coming into the main wash. Here you are only digging through the current flood layer and testing for flood gold. Make your way out of the wash carefully looking at the bottom of the tributary and the areas where the water flowed into the tributary. Look closely for jagged bedrock and slight lifts in the ground and then prospect. Continue to test each of those spots. What started as a few specks of flood gold in the main wash can lead to larger and larger deposits on the flats or in slight inclines across the desert floor. Keep in mind that when a flash flood is dissipating, there is not enough energy to move a lot of rock, but the sand will continue to flow a bit, creating great clues.

In general, cool season precipitation (October through April) is the most extensive source of rain in the desert regions. Rainfall is more widespread and of relatively long duration during the cool season. On the other hand, warm season precipitation (May through September) results largely from short monsoon-type thunderstorms.

If you’re ready to head to a sunnier climate this winter, keep these tips in mind and you just might find enough similarities between water and desert mining to make you return every year.  Good luck!

Posted by: Denise AT 08:51 am   |  Permalink   |  Email
Friday, September 30 2022
In an area either rumored or known to hold gold, where should you look first? The creek, the surrounding hills, washouts, or just where? The characteristics of the gold in that area will help you to know where to start. If the gold is flat and pounded, that indicates it’s been in the water a long time. If the gold is coarse and chunky, you know you’re getting closer to the source. When gold is smoother, stop and go back to the coarsest gold and start working upwards until you find the source.

Keep in mind that gold is gold, so there isn’t necessarily a better type of gold. Some is just easier to recover. There are only two typesgold nugget of gold deposits. The first type is “lode” which is simply everything that is still in the matrix and in the ground, and the other is “placer” —or everything else.

Lode deposits refer to gold that is still locked within its original solid rock formation. This formation of gold generally starts as a vein in rock and is formed over millions of years. Since the gold is locked up in rock, and can be mixed with quartz, calcite, pyrite, and other minerals, lode gold  usually requires specialized mining techniques to extract. Lode mining takes a lot more equipment and generally a lot more expense and is usually undertaken by large commercial operations instead of the average prospector. Placer gold is the gold that most prospectors are more familiar with. Placer gold isn’t really any different than lode gold. It is simply a concentration of that same gold that has eroded and traveled away from the vein.

Since gold is very dense, it will move downhill much slower than the surrounding sediment. It tends to become concentrated on or near the surface of the lode, forming a “residual placer” close to the original bedrock exposure. Gold found downhill from the immediate outcrop above the nearest watercourse is called an “eluvial placer.” Once it reaches the nearest waterway and is transported by flowing water, the gold now is known as “alluvial placer.”  The origin of the dust, flakes and nuggets found by panning and sluicing is usually from a vein up on a nearby mountain.

Bench placers were originally stream placers. Benches are simply where the water used to be, maybe even millions of years ago. They are formed by erosion or geological events such as uplifts, earthquakes or plate drops that changed the stream flow. Some of the most profitable mining is performed on benches. Many benches are highly concentrated by the alluvial deposits that still feed them.

Stream deposits are the last resting place for gold. Once the gold has been released from the lode, gravity and nature does the rest. And unless gold gets stranded on a bench, it will find its way to the water someday. It may take a million years, but it will get there.

When deciding where to begin prospecting, most of the time you’ll want to start panning in a water way, or a wash in the desert where water once flowed. Then let the gold tell you where to go from there. When the gold gets coarse and ragged, start to move up, looking in reverse of how it got to the spot where you found it. In addition to panning and sluicing you may wish to upgrade your mining efforts with a highbanker or power sluice, dredge or trommel. Moving soft soil or river gravel is obviously much easier than breaking rock, but for small scale miners, a rock crusher can pulverize 2 or 3 inch sized rocks into powder in no time. Move more material faster— get more gold! 
Posted by: Denise AT 01:00 am   |  Permalink   |  Email
 

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