Friday, October 29, 2010

More on Gold Prospecting: Modern Methods (Part 1)

(Photogeologic image.)

Modern Prospecting Methods

To date you've heard me talk quite a bit about the oldtime prospectors and some of the indicators they looked for out in the field. However, many modern prospecting surveys rely on methods and technologies that were only dreamed of by those single-blanket, jackass prospectors of old.

Where to Find Placer Gold

This is especially true where larger mining operations are concerned since much of the gear associated with modern prospecting is costly and sometimes unwieldy. Here are some of those modern prospecting methods and technologies:


Photogeology is a very important facet of modern prospecting and is employed by most mid-to-large scale gold mining companies today. This prospecting method relies heavily on aerial surveys and satellite digital imagery where real color, black and white, and infrared images are compared.

These color comparisons of large-area images are then analyzed to determine where mineral-rich outcrops may exist in highly vegetated zones. Photogeologic images are also very helpful in identifying changes in vegetation or rocks and soils which are often strong indicators of gold mineralization.

(Note: In my previous post I mentioned the importance of color and earth/soil changes in identifying potential gold mineralization. See? The oldtimers knew their stuff long before the advent of all these fancy technologies we have today. J.R.)

The obvious advantage of using photogeology as a prospecting tool is that you can cover vast areas covering hundreds (or even thousands) of square miles at one fell swoop. Now here's a tip for you: there are a number of venues online (including Google Earth) that are closely related to photogeology and that may prove beneficial to the "arm-chair" prospector who doesn't have a big bankroll.

Seismic Refraction/Reflection

Seismic refraction/reflection is a geophysical prospecting method widely used for exploring what may exist underground. Seismic refraction/reflection goes something like this:

When seismic waves are generated they travel outward from a source until they reach a detector like a seismograph. The detector first picks up the seismic waves that traveled to it along the surface and subsequently senses any seismic waves that may have traveled downward and were refracted (broken up) at depth. These deep waves will eventually return to the surface.

Since seismic waves travel faster at depth they easily overtake any surface waves and at fixed distances these "refracted" seismic waves reach the detector first. With this initial seismic information certain assumptions can be made about the thickness of existing surface layers and their potential composition.

Mining Equipment
Gold Concentrates

If you're wondering just how the hell this can be of value let me explain. This information can tell you about local bedrock topography; help you determine the depth of existing gravel overburden; delineate water tables; detect subsurface caverns or "pockets;" identify shallow faults and fracture zones; and even indicate where large boulders or obstructions exist underground.

Now you can see how seismic refraction/reflection could be of great benefit in "profiling" a given lode gold or placer location. Getting back to the bedrock topography angle, this method will even indicate where bedrock in underground channels is fractured or contains cracks or crevices! Imagine this method employed in a Tertiary Channel ("prehistoric rivers of gold").

These are just two of many modern prospecting methods and it should be readily apparent how effective approaches like these can be, especially if they are employed in combination. I'll have more for you on modern prospecting methods in my next post.

Be safe until then.

If you liked this post, you may want to read: "More on Gold Prospecting"

(c) J.R. 2010

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