A small cloud of dust coming from over the next ridge caught my eye. I pulled off my detecting headphones and listened. A faint but continuous hum, almost like the whirl of a chainsaw floated on the still air. My curiosity got the better of me and I couldn’t resist hiking towards the sound. As I reached the top of the ridge I spotted a man shoveling into a wooden device which appeared to be powered by a gasoline engine. Both man and equipment were enveloped by a thin cloud of dust. After a few moments he spotted my silhouette against the skyline and paused from his shoveling. He waved hello and motioned for me to come down. Turned out he was a prospector as well and getting good gold, not with a metal detector, but by shoveling it into his homemade “shaking” device. This was my first experience with a wonderful piece of prospecting equipment known as the drywasher.
For those unfamiliar with this piece of mining equipment, a drywasher is essentially a device used to separate particles of gold from dry dirt, sand or gravel. No one knows for certain when the first drywasher was developed, but it has been said that Thomas Edison experimented with a dry-process gold machine in New Mexico as far back as 1897! Their ability to sort gold from soil without the use of water may seem trivial in comparison to the multitude of high-tech devices we have today, but for early gold seekers it was a revolutionary breakthrough. For the first time in history placer miners had an effective tool for working the arid goldfields of the southwestern United States and Western Australia. These ingenious inventions have been used successfully to recover the yellow metal for well over a century, and continue to be one of the most popular pieces of mining equipment used by recreational prospectors.
Although there are variations, most drywashers consist of two boxes and a folding four-legged frame. The upper box is called the “hopper” and is fitted with a wire screen (or grizzly), while the lower box is fitted with riffles and is referred to as the “riffle tray”. Unlike a sluice box which relies on running water to sort gold from worthless overburden, the drywasher uses currents of air. There are two types of drywashers in use today; those which use bellows and those which use a small blower motor.
Hand cranked models are powered by the operator and use a system of bellows to deliver “puffs” of air which vibrate the gold-bearing material across the riffle tray. The lighter material passes out of the tray and onto the ground, while the heavier gold particles are trapped by a dead air space behind the riffles. The more modern blower motor powered (or constant air) models are equipped with a fan offset by a spinning counter-weight. Instead of “puffs”, a constant stream of air is pushed through a hose by the blower which then causes the unequally weighted fan to spin, effectively shaking the riffle tray. The lighter material passes out of the tray and onto the ground, while the heavier gold particles are trapped inside the riffle tray by the vibramatic/electromagnetic action.
Drywashers are an excellent choice for those looking to get gold from the desert regions found in Nevada, Arizona, New Mexico, California, and Mexico. Unlike the cumbersome devices of yesteryear, the modern drywasher is fairly portable and easy enough to be worked by a single person. Before making a purchase, perspective buyers should consider which type and size drywasher will best suit their needs. The bellows type drywashers are much quieter and don’t require expensive gasoline to run, however, they cannot process as much material and are more labor intensive. The blower motor type can process about double the amount of material in a single hour and will save a person’s arm from cranking, but they are considerably louder and require the use of a 2-stroke engine. The size of the drywasher chosen is also important. The smaller units are more compact which make them great for sampling in remote country; however their processing ability is limited. Larger units are heavier and less portable, but they are able to handle a considerable amount of gravel. When in doubt, my suggestion would be to go with something in the middle. The following are just some of the companies that manufacture quality drywashers: Keene Engineering, Gold Buddy, Thompson Drywashers, Gold Duster, and Pack Washer.
In addition to the drywasher itself, some of the other equipment you’ll need to pack along is: a shovel, pick, 5-gallon bucket(s), gloves, dust mask, basic hand tools, gold pan, several gallons of water, panning tub, and spare gasoline if you are using a blower motor. If you get really serious about dry-washing there are two other items which I’d highly recommend. The first is called a Vac-Pac. This device is a gasoline driven vacuum which is used for sucking out the gold from bedrock cracks and crevices. I have been using one in conjunction with my drywasher for years with excellent results.
The second item which I never go drywashing without is my metal detector. Before leaving my diggings, there are two places I scan with a detector: the header pile and the hole itself. The header pile is composed of the larger overburden that wouldn’t pass through the grizzly, and it is here that big nuggets can get accidentally deposited. Often they are encased in a dirt clod and roll off the screen, or the operator simply fails to see them because of the dust. I have found many nuggets over the years in header piles. The holes I dig while drywashing are another place I never neglect. Even if a person digs down to bedrock and uses a Vac-Pac, there may still be nuggets lodged down several inches within a crevice. Using a metal detector to scan your hole will ensure that you’re not leaving them behind for someone else.
Before heading out to the hills with your drywasher, be aware that there are some common mistakes made by new owners. I know about them because I made them all myself…numerous times. First and foremost, is the speed at which the drywasher is fed. My early drywashing motto was simple: shovel as much material in as fast as possible. My thinking was that the quicker I fed the dry-washer the more gold I’d ultimately have at the end of the day. Reasonable logic, but as I discovered, not always true. Overloading the machine with too much material will not allow it to do its job properly. The riffles will become swamped and a good portion of what was just shoveled in may end up back on the ground. The problem is further worsened if the riffle tray is angled too steep. This is easily fixed by running a few shovels through in the beginning to test the riffle tray angle. If the dirt whips through in a matter of seconds, it is probably set too steep. If the dirt moves through the tray like molasses, it is probably not set steep enough. Find an angle somewhere in the middle and set a shoveling pace that will give your unit adequate time to effectively process the material.
Another problem all drywashers face is soil moisture. If the dirt being processed is completely dry it will easily flow across the riffle tray and produce the tell-tale dust cloud. Wet soil, on the other hand, will clump up and move sluggishly across the riffles and produce very little dust. This will hamper gold recovery allowing all but the largest of particles to slide over the riffles and onto the ground. The wetter the soil the worse your gold recovery will be. If the soil is completely saturated I would suggest you put the drywasher back in the garage and wait for the ground to dry out. If the soil is damp, a person can try spreading the wettest of the material on a plastic tarp and letting it dry in the sun. It is also a good idea to rerun the tailings coming out of the riffle tray back through the drywasher. Whatever gold was lost on the first pass through will have a second chance to get caught. Although time consuming, it does work.
You will also want to periodically shut down the drywasher and do a clean-up of the riffle tray. The dirt being shoveled into the unit will most likely contain black sands. These iron-rich sands, like gold, are fairly heavy and will become trapped behind the riffles. If too much black sand accumulates, you run the risk of overloading the tray and allowing some gold to slip past. As a general rule, I like to clean out the tray approximately every 30 minutes. Frequent clean-ups will not only ensure maximum recovery, but it will also let you know if the area you are working warrants further digging. If the showing is poor after a few runs you might want to consider relocating to a new spot.
Because a drywasher works best when the dirt is bone dry, you will most likely be using one during the warmer summer months. From May-August, temperatures in the desert often exceed 100 degrees, so you will need to take certain precautions to ensure your safety. Try to work in the early morning or towards evening and avoid the mid-day hours when the sun is at its peak. Take frequent breaks and drink water even if you don’t feel thirsty. Wear a wide brimmed hat, a long sleeved shirt and lather any exposed parts of your body with sunscreen. The only thing worse than being exhausted and dusty is being exhausted, dusty and sun burnt!
Drywashing is hard work, no two ways about it. It will leave your hands blistered, your muscles sore, and in most cases have you blowing brown gunk from your nose for at least a day! Okay, not the most glamorous method of mining, however if someone were to ask me if I would prefer a good day at my normal 9 to 5 job, or a mediocre day of drywashing, I’d choose the latter every time. It is an incredibly rewarding pastime that will help relieve stress, keep your body fit, and ultimately put valuable gold in your poke. Those persons planning an expedition into the desert goldfields will want to strongly consider adding a drywasher to their prospecting arsenal. It remains today, just as it was a century ago, one of the most effective tools for recovering gold from a dry-placer environment.
I wish all of you the very best of luck with your prospecting! For more information on searching for gold, please visit the author’s website at: www.ArizonaOutback.com.
Straight, Jim (1989). Successful Drywashing. Rialto, California: Self-published.
McCracken, Dave (1993). Gold Mining in the 1990’s. Northridge, California: Keene Industries.