As an Amazon Associate, I earn from qualifying purchases with no additional costs for you.
Rockhounding is a fun, exciting, and rewarding way to enjoy the outdoors. You just need a sense of adventure, a keen eye for details, and the right tools, such as a Geiger counter. These simple devices can lead you to interesting places and rocks, provided you know how to use them.
Geiger counters are simple devices that are easy to use. They all convert radiation into an electrical current that you can use to measure the intensity of the radiation. The exact mechanism for this will vary from device to device, but they usually just beep when they get a hit. You can then use a watch to count them.
Depending on your budget, you can get counters to do the counting. It all comes down to knowing which features you want when picking a Geiger counter for rockhounding.
If you want to check out the best Geiger counters for rockhounding, you can find them by clicking here (Amazon link).
How to use a Geiger Counter in Rockhounding
Rockhounding lets you explore the natural environment in ways no other hobby can. You get to see the finest gems, fossils, minerals, and rocks nature offers on top of the many benefits of hiking. You just go out there and turn over every rock.
You do not need any training or experience to do it either. You can head to a nearby creek or roadcut to begin your career as an amateur geologist. Rockhounding is one of the cheapest hobbies, as you do not need fancy equipment.
However, finding the best rocks becomes increasingly difficult as the hobby grows. You must rely on tools sooner or later if you want that rare find that you must add to your collection.
Luckily, most rockhounding tools are simple and easy to use. Most are specialized hammers, brushes, and chisels, but these tools can only get you far. You need a Geiger counter if you want to see if a spot is worth digging.
Geiger counters measure the radiation in an area. As many minerals are radioactive, these devices let you identify which minerals are in which rocks. They even detect radiation sources inside walls, making them versatile for finding rare gems.
Radioactivity for Rockhounding
Because Geiger counters deal with radiation, a basic understanding of radioactivity is needed to understand what the devices tell you. However, you don’t need to go deep into the subject for rockhounding. You just need to know the radiation you will find in the field.
Radiation is everywhere, making it an interesting property of minerals. You can find it from space, from man-made sources, and from the natural environment, though you only need the geological environmental radiation to collect rocks and minerals.
Rock minerals produce radiation as particles and energy rays as they decay or disintegrate into other minerals. This radiation takes the form of alpha or beta particles or gamma rays emanating from the source rocks.
- Alpha particles are high-energy, positively charged, low-mass particles.
- Beta particles are either negatively charged electrons or positively charged positrons.
- Gamma radiation is high-frequency, shortwave waves of light energy.
Uranium, thorium, Carbon-14, and their daughter elements (or decay products) produce most of the radioactivity found while rockhounding.
You’ll find trace amounts of them in granite and other igneous rocks. These rocks come from deep into the Earth’s mantle and core, where they are responsible for most of the internet heat. Geiger counters let us find the sources of this radioactivity for both safety and pleasure.
TIP: There is a good chance you have collected a specimen with radioactivity while out rockhounding without knowing it. Find out common radioactive minerals in the article below:
What are Radioactive Minerals? 6 Common Radioactive Rocks
Geiger Counters Count Radiation Intensity
Geiger counters replaced large stationary contraptions that detected and counted radiation through photographic plates and fluorescent screens.
While some of these devices feature improved technologies, such as gold-leaf electroscopes and piezoelectric-quartz meters, they were too bulky to use in the field without great effort and expertise.
That changed when Has Geiger and Walther Muller invented the Geiger counter in 1908. His sealed, thin metal tube with a wire through its centre let geologists make discoveries they could only dream up a few years before.
Today’s devices have shrunk the technology to the point where they can fit in a shirt pocket, opening the world of geology to everyone.
While the actual design will vary between devices, all Geiger counters measure the amount of radiation that passes through a sensing element housed deep in the detector.
You can configure this sensor for any of the three types of radiation, giving you a full view of the target’s radiation spectrum.
The sensor is a closed cylindrical tube containing an inert gas such as Neon, Helium, or Argon under low pressure. A high voltage exists across the ends of this Geiger-Muller tube.
The gas remains non-conductive until radiation strikes it to produce ions, which create a pulse of current under the influence of the voltage. It is this electrical pulse that the counter reads to give the results.
Geiger Counter Operation
Geiger counters read the radiation pulse differently depending on the device’s circuitry. Generally, a counter only counts pulses once the radiation rises significantly above a threshold. Otherwise, it remains silent to prevent false positives.
Depending on your device, you may just hear a clicking sound or “tick” for each hit in the detector, or you can read the value off the display if one is present. Just make sure you have a timer to count the ticks if you must do it manually.
A counter’s threshold is typically set to the region’s nominal level, varying between 15 to 25 CPM (counts per minute). If this condition is met, the counter makes a clicking sound.
This threshold is either set by the hardware in the device or through a configuration setting on the device. This setting defines the length of the tube.
A Geiger counter’s sensitivity is also proportional to its size. A bigger tube lets more radiation inside, enabling the device to support lower thresholds. With a long enough tube, you can even detect low-level radioactivity.
Some advanced counters will even let you change the read-out units, such as CPM, micro roentgen per hour, or micro Sieverts per hour.
A few will let you set the count timer. It all depends on the features of your counter, and you should ensure you understand what it can do before you do anything else.
TIP: Earthquakes are caused by plate tectonics in which two or more portions of the Earth’s crust interact to cause stress buildup in the surrounding rocks. Find out common rocks you can find in earthquake zones in the article below:
Eight Most Common Rocks You Can Find In Earthquake Zones
Reading a Geiger Counter
If you are lucky, your Geiger counter will compute your rate. If this is the case, you can just walk through an area or hold up rocks until the device shows something interesting.
However, personal counters which do more than just display a count are rare and expensive.
Most consumer-grade counters require some manual operation. Therefore, you should always take a good watch or timer on your rockhounding journeys. That way, you can ensure you can always find good hot spots wherever you go.
You generally have two modes of manual counter operation.
- Listen for peaks in the ticks.
- Count ticks over a set period.
Both operations offer different information about the rocks at hand, giving each method a specific purpose:
Listening for Peaks
Listening to the ticks is the easiest of the two modes. You just listen. You can walk around the field until you hear the ticking increase dramatically, but you do nothing else. The increased intensity may indicate an interesting rock formation or specimen nearby.
Once you reach the right spot, you must switch strategies, but by then, the hard part is done, and the fun begins. The rocks you want are beneath your feet, waiting for you to unearth them.
Counting the Ticks
The other method is more involved and thus is more recommended for analyzing individual rocks. This mode requires finding the actual intensity rate of the radiation, which you can do manually or digitally if available.
Manual counting requires listening, counting each tick throughout a period, and then doing math on the result. Digitally, it just means setting the counter’s timer setting and then reading the results as they come up.
Regardless of your situation, counting ticks requires syncing the Geiger counter to a timer for at least five minutes. The period you use matters little here.
You’ll want something you can easily use to compute the rate. Once everything is synced, you can press the counting button on the counter to begin taking measurements.
Once in counting mode, a Geiger counter is mostly hands-free. You can place it near where or what you want to be measured and then let it do its thing.
The device will continue counting until you stop it or the timer runs out. At the end of the run, you can read the total count of the device. The number may jump before then, but only this final value is important.
If your device does not do it for you, you can divide the result by the time to get the target’s rate or average radioactivity.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
Interpreting the Results
A Geiger counter’s result will tell you how intense the radiation is but cannot tell its type. If this is all you need, you are good. The device will direct you to where the good rocks lie as is.
However, if you need more information, you need more work. The small differences between the radiation types offer great insights into the composition of things, letting you know you found something truly intriguing.
Fortunately, most of the extra you need is simple. For instance, if you want to know if your rock releases beta or alpha particles, you can repeat the count after covering the rock with wood or aluminum.
Wood only blocks beta particles, while aluminum blocks both. Thus, you know the radiation type if your counter only reads ambient noise or not.
If the readings do not change regardless of covering, you know it is gamma radiation. Otherwise, the rock radiates in multiple forms if the values change with each covering. You can also use paper to check alpha particles in a pinch.
If you do not have enough covers, you can subtract the values for the covers you do have to get the appropriate rates.
Where you go from here is up to you. While Geiger counters only provide radiation intensity, those numbers can lead you down adventures you never thought possible.
They can point you to precious metals, rare fossils, and other hidden treasures, especially if combined with a reliable source of radioactive materials for your area.
TIP: Be sure to stay safe when you rockhound. I encourage you to read this article on recommended safety equipment & tips for rockhounding here:
Recommended Safety Equipment & Tips for Rockhounding!
Choosing the Right Rockhounding Geiger Counter
Because Geiger counters are simple devices, most considerations for picking one for rockhounding often come down to personal choice. You do not have all the bells and whistles to collect rocks. A good, reliable counter which can display the count is all you need.
Still, those extra features may come in handy in the field. Plus, a counter’s construction can heavily impact its sensitivity. While you do not need a professional grade counter, a good, reliable one that can do the math for you works great when you are in the middle of nowhere.
While these features can vary, there are some common characteristics for a reliable personal Geiger counter. These characteristics can help weed through the vast array of counters out there of every shape and size.
These characteristics include:
- Price
- Speakers
- Size
- Battery life
- Fits Your Tool chest
- Compact design
- Ease of use
Pick a Geiger Counter You Can Afford
Price is always a major concern when it comes to rockhounding gear. You want a counter you can buy and still have enough left over for your trip to the wilderness. Also, the higher-priced counters may come with features you will never use.
A good start is establishing a budget and only looking for counters under your price range. Just remember to account for the costs of your other gear, such as picks and travel expenses. Rockhounding ventures can get expensive quickly if you are not careful.
When looking for a budget-friendly Geiger counter, I recommend trying Meterk EMF Meter Electromagnetic Field Radiation Detector, which you can buy on Amazon here (Amazon link).
You Must Hear the Geiger Counter
The clicking sound is why you bring Geiger counters on rock-hunting excursions. The sound warns you of any nearby radioactive materials.
A faint click can go unnoticed. Thus, you must be able to hear it regardless of anything else that might be in the area. A good counterspeaker can grab your attention wherever you put it.
Pick a Geiger Counter You Can Carry
Larger Geiger counters are more sensitive but are useless if you cannot carry them. Remember, you must carry all your gear and any specimens you find. Thus, you want a compact enough counter to carry and store easily.
However, you want to evaluate where you want the hobby to take you. You lose accuracy if you go too tiny. Therefore, you must strike the right balance for your needs. Something large enough to find what you want while small enough to fit your lifestyle.
The Better Must Last Your Trip
A dead battery makes a Geiger counter useless. All counters need something to supply the sensor voltage. Therefore, you want a counter and battery pair you can count on to be there for you.
Fortunately, you do not need a counter with a powerful battery. You just need one that can last your trip. Fortunately, personal Geiger counters tend to have great battery life.
Most counters can go for an entire day on a single battery. You may even find a few counters which only require AAA batteries.
Select a Geiger Counter That Works with Your Gear
Good rockhounding requires more than just a good Geiger counter. You need quality pickaxes, brushes, and other jewelry equipment as well.
You need these tools to remove the rocks from the ground, which are on top of the covering material and the watch you need for your counter. Therefore, you want a counter that will fit well with your kit.
TIP: Another great tool that can help you with rockhounding is a metal detector. I wrote about how to use a metal detector to find gems, you can read from the link below:
How do you actually find gems with a metal detector? It is Easy!
Simple, Compact Designs Work Best
Rockhounding is more fun when you can concentrate on the rocks. If you need to read the manual every time you run your Geiger counter, it is probably too complex to use.
You also want something you can easily carry and read. A bulky counter can lead to missed opportunities and headaches.
The best Geiger counter I can recommend to you is the Geiger Counter Terra-P. This Geiger counter is used by some armies worldwide, and it is one of the most popular among professionals. You can buy it on Amazon here (Amazon link).
Pick Something Easy to Understand
You are not a professional geologist or nuclear scientist. Therefore, you should never get a Geiger counter that gives more info than you need.
You also want something you can control with just a few clicks. So, keep your gear simple and as accurate as possible.
Final Thoughts
Rockhounding is a rewarding hobby that can show you the world, literally. It takes you on a journey to Earth’s past with the finest rocks, minerals, and fossils out there.
It is all out there waiting; a good Geiger counter can guide you. These simple devices can point you toward any ionized minerals waiting to be discovered. You just need the right one for you.
TIP: When you are looking for other equipment for rockhounding, check out my articles about all the recommended tools you will need:
Recommended Rock Hammers, Picks, Chisels & Bars For Rockhounding
Recommended Dichroscopes, Hand Lens, and UV Lamps for Rockhounding
Best Shovels, Brushes, Sample Bags & More for Rockhounding