Rock Hounding and Rock Hunting
Another outdoor activity my kids and I often engaged in is hunting for rocks. We would search through literature, study mineral distribution maps and compare findings with topographical maps, plan excursions, and wander through the hills looking for the telltale signs of mineralization looking for gemstones and crystals and the coveted geode.
I have been interested in rocks since I was a kid. The tools available today are vastly superior to what was available in the past. There are internet sites with information about identification of materials, topographical map programs, GPS, and newly developed field assay tools that make identification of materials far easier.
Going out in spring to explore freshly eroded stream bottoms and banks, or hillsides, and newly fractured rock faces increases the chance of discovering previously hidden deposits.
Successful rock hunting requires a fundamental knowledge of mineralogy and geology, as well as geography, a good deal of observation, walking and probing, and diligence.
Read the literature first. There are many websites that provide various levels of information. There is plenty of information about where to look and what to look for. That’s a good place to start but remember that if the location is published it will likely be more heavily picked over. Exploration for undiscovered deposits and finds could yield the highest potential value. Then again, even in areas highly searched, undiscovered deposits could be just beneath the surface.
There are many sophisticated tools available to identify potential deposits beneath the surface such as ultrasound, radar, x-ray, metal detectors, and other imaging and detection instruments. Equipment with the best potential for success is more expensive.
Then again, a lot of what sophisticated equipment detects can be detected using simpler methods. The most common tools are a shovel, a hammer, a screen, a pan (and/or a bucket), a chisel, a magnifying glass, and a pocket knife. There are other useful tools for sampling, sorting, identification, carying, and recording finds and locations but in my travels the tools listed above are the tools I have found I use most frequently.
A geologist’s hammer with a pick on one end is handy but a claw hammer works almost as well. A pick is the quickest and handiest way to probe. A better quality tool will require far less maintenance.
A shovel is necessary. A folding Coleman trenching tool with the independently folding pick and shovel is pretty cheap.
A chisel is very helpful. A lightweight hard alloy rod with a chisel end can double as a bar, and is useful for "sounding" rock faces.
A spray bottle with water and perhaps vinegar, and brush to clean samples for visual observation is handy, if not essential, particularly in areas where no water is available. A spray bottle concentrates small amounts of liquid in a small area with some force. A pint of liquid in a sprayer can last a long time. The acidic vinegar dissolves some mineralization and brushing and spraying carries sediments away. It’s quick, easy, and cheap.
As far as detecting materials and voids beneath the surface is concerned, the tools you have can be used with development of certain skills. Different materials sound differently when struck. Using the geologist’s pick can produce some audible differences as well as indication of hardness. Rocks ring, voids sound hollow. The difference is unmistakable. Practice makes perfect. A more accurate method is to put the rod at a point in the rock or formation and press your ear on the other end striking around the area with the pick. It works like a stethoscope but louder if done properly. The sound carries unimpeded through the rock and rod and is significantly amplified to the ear. The sound of the striking of the rock with the pick can be heard in a radius depending on the type and makeup of the material. Subtle differences heard can indicate what is below the surface. Again, it takes a bit of practice and experimentation to be able to pick out what the subtle differences in sound indicates. The basic fundamental is that harder substances produce a more distinct ringing. Voids have a distinctive double hollow sound. Soft material beneath the surface produces a more subtle muted hollow sound.
Conversely a sharply increased ringing sound in an area of more muted sounds could indicate the existence of a harder crystal deposit hidden beneath the surface.
In weathered or loose or consolidated aggregate deposits a listening rod pounded solidly in the soil can be used to differentiate the sounds from striking the surface with the hammer end of the geologist’s pick. The sound will be a dull sound. What you’re listening for is something different from the average sound. The difference in sounds from various conditions can be quite subtle but distinguishable if listening carefully.
Another handy tool is a compass. A compass can indicate iron content. A cheap metal detector is even better. A small detector is good for rock hounding but a fancy expensive computerized model is not necessary. A small compact detector, preferably with a discriminator to differentiate between ferrous and non-ferrous metals works fine with some common sense.
Another tool is a screen or better yet, a set of two, maybe three screens of graduated sizes to sort material by size. Larger rock can be assessed by visual examination. Screening out the finer material for further processing saves a lot of time. The screens don’t necessarily need frames if keeping weight down is a consideration. A pan with large slits to catch big rocks is called a grizzly.
A rudimentary collection of tools to assay or determine physical properties of materials can be easy to assemble. A nail, a file, a piece of glass, and a piece of fired unglazed ceramic tile for a streak plate, a strong magnifier, maybe even small bottles with eyedroppers of weak acids and dyes, a compass, and a handbook with properties of minerals and metals with photos provide most of the tools needed to identify rocks and materials. Polarized sunglasses can be helpful to in analysis. A handheld black light is necessary for positive differentiation between some minerals and makeup of various rocks. It’s not necessarily essential for questions of high probability but useful for some definitive identification. A black light is also fun to search for fluorescent and radioactive mineral deposits at night. A very small two frequency light costs a bit but miniature ones are available for as low as twenty five dollars.
Another useful tool is a gravity water separation tube described in my article about panning, or a miniature version using a clear bottle for the tube with an eyedropper to deliver the water for agitation and sorting by density. Using a miniature version conserves weight, size, and resources. The chemical makeup of materials can be narrowed down by sorting in a mixture of materials of varying density, making it visible by dying it with a fluorescent dye. The mixture should be known quantities of several layers of various materials with known density such as aluminum chips, silica sand, and filings, copper filings and B-B’s, stainless steel chips and filings, and lead chips and filings, dyed with different colors. If you have a black light the dye will fluoresce showing where in the stratified layers of increasing densities the material ends up after sorting. If the formation is large a representative sample can be crushed to aid in making the assessment. The crushed and dyed sample will show up somewhere in the layers. If you know how many layers the testing mixture has and what the densities of the materials are, the density of the sample being assessed can be obtained in a range between adjacent layers.
A conservative collection of tools can be assembled to fit in the small zippered compartment of most butt packs. If you're like me though, a small knapsack is necessary. I am usually overprepared but by the same token I am rarely underprepared.
In stratified layers, crystals form most frequently beneath the harder layers. The softer material erodes away leaving room for crystal formation. The crystals usually form where water can flow leaving layer after layer as the void increases. Fissures, voids, and bubbles in volcanic rock, and sandstone or limestone deposits are where crystal formations develop and sometimes eventually fill up leaving large crystalline deposits embedded in the rock.
Aside from support equipment to provide the necessities and comforts of life, the actual equipment for successful rock hounding is relatively small. The weight can be kept below five pounds if you consider the Coleman trenching tool to be a piece of support equipment and you would normally have a small hammer anyway. A knife and compass are wise things to have in the field irrespective of any prospecting activities. Many of the tools used for prospecting are normally carried in the field for hiking and packing.
Go to Part 4
Pictures of Rocks and Stuff
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