Fine Gold Recovery With a Blue Bowl Concentrator
This Makes Placer Gold Prospecting Easier
Separating the Fines
No doubt you have heard the expression "separating the wheat from the chaff." It refers to separating the valued material from the husk. With regard to amateur prospecting, the work of separating gold from iron, or black sand concentrates, is similar. We want the gold, but trying to get it out of a mix of concentrates is tedious. My favorite instrument for this is the renowned Blue Bowl.
“Like a lot of things in life, it’s the quest, the seeking of it,” Chester says, quoting Robert Service, the poet of the Yukon: “It isn’t the gold that I’m wanting so much as just finding the gold.”
Water Power Is Precious, Like Gold
Water that is pumped into the bowl drives the lighter material swirling up and through the hole at the top center of the cone. The bowl in its entirety resembles a bundt cake pan. The tower (cone) base is where the fine gold is collected.
The bowl sits on a bucket (3 to 5 gallon) which gathers the drained water and black sand. Most utility buckets will work just fine. If the lip of the pail is too big for the levelers, you can trim it a bit to fit. Because it is important for the bowl to be level, clips can also be purchased to adjust the attitude of the bowl. To level, I usually place my bucket on a large concrete paver that is flat and adjust the bottom of the paver. You can also buy a recirculating pump that can be run off of a 12 volt battery. In this case, you would put the bucket with the bowl in a tub - 18 gallon is good. This is very handy in the field, especially the desert, as the water overflows the pail and is harvested.
The Physics of the Thing
By limiting the amount of force required to lift the sands, the better the bowl works. Therefore, making the bowl level is extremely important. There are two force vectors involved in lifting the concentrates you don't want and leaving the gold on the bottom. The weight of the gold guarantees it will be left at the base. The force of gravity assures this, as gold is the heaviest element in the paydirt. The force of the water entering at the side pushes the lighter material; as the water force exceeds gravity, material is lifted. There is a valve on the outside of the bowl that allows fine adjustment. You open the valve just enough that the concentrates, or cons, swirl and lift and the gold remains. Watch all of the material and continue to open the valve more, but watch the speed at which the cons are rising and look for your gold - not so fast that your gold washes away. It's easy controlling the valve while watching this dynamic unfold.
Finer Can Be Easier
Of course, the size of your concentrates will determine the speed with which the bowl separates material. In general, the larger the granules, the heavier the material, and the more time it will take to sort. So you want to classify the material well. Classifying to 30 mesh is good - 50 mesh is also advised. It is whatever you prefer. All mining and prospecting stores carry classifiers of various sizes. Classifiers can also be found on line. I made mine out of screen on wooden frames.
You can use a regular garden hose, or you can buy plastic tube to run off of your pump.
Before starting to pump water, add your concentrates to a full bowl. I use a large spoon to thinly cover the bottom of the bowl all the way around. Then start your water and pump.
What's All This Talk About Jet Dry?
A little Jet Dry or dishwashing detergent in the water reduces surface tension. Surface tension is a phenomenon in which the surface of a liquid, where the liquid is in contact with gas, acts like a thin elastic sheet. When the liquid surface is in contact with gas (such as the air), this tension allows insects denser than water to float. It also allows the lightest of gold particles (also called oat gold or flour gold) to float. Using a drop or two of detergent keeps this from happening. We want all of the gold to congregate at the bottom of the bowl.
If you want to do the very best job collecting your tiniest specks of gold (I mean tiny!) be patient and run the water slowly for a longer period of time.
Once the black sand has been washed away, you will see your yellow gold. Use a snuffer bottle to retrieve the gold. These bottles are also known as sniffer bottles. They are 2 ounces in size with a screw top and a tube down the center of the bottle. Squeeze the bottle and release when the tube is in the liquid to pull up the gold. You can twist and turn the bottle in any direction and it will still suck up material, and won't leak upside down.
When you want to put your gold into a vial for safekeeping, I put the gold and water from the snuffer into a pan. With a suction tweezer I draw the yellow gold up and then drop it in the vial.
Gold flake or dust collection vials are small. They are typically 1/8 ounce to 1/2 ounce and made of plastic or glass. I prefer the plastic - it's easy to drop a vial in the field and break it. For that matter, it's easy to drop one at home risking the loss of your flake. Believe me, I have done it. It only takes one clumsy move to make you a convert. Stay away from the type that has a cork top.
The water and the vials magnify the size of the gold flake. After so much work, it is fun to look at your gold in detail. Besides, when you are looking at "larger" flakes, it helps to reduce gold fever!
The Names Say It All - Conclusion
Oat gold, fine gold, micron gold (micros), and gold dust are all terms used for the smallest forms of gold. These minute particles get lodged under rocks and pebbles and collect on the top of bedrock. They originate from lode gold upstream that breaks apart and is washed downhill. The farther the gold tumbles, the smaller the fragments get.
Small scale prospectors are always looking for tools to reduce the work involved in washing paydirt for the ultimate goal of yellow gold. The Blue Bowl Concentrator is just one of many ingenious mechanisms for making life a lot easier for prospectors.
Dyer C. (2012, July 01). There's Gold in Them Thar Hills! Retrieved from https://www.atlantamagazine.com/great-reads/north-georgia-gold-rush/
King H.M. (2005 - 2018) Brains are the Keys To Finding Gold, The Most Important Prospecting Tools. Retrieved from https://geology.com/articles/gold-prospecting-tools/
Kirkemo, H. (2016, November 30). Prospecting for Gold in the United States. Retrieved from https://pubs.usgs.gov/gip/prospect2/prospectgip.html
Questions & Answers
© 2018 John R Wilsdon