The Pan-American Mineral Jig: Building a Duplex Round Jig
The modern mineral jig or gravity concentrators have their foundation firmly rooted in ancient history and are considered to be one of the oldest mechanical device designed specifically to recover heavy minerals from lighter gangue material. During the development of the Wilfley table in the 1890’s to the innovative and successful flotation techniques of the 1940’s mineral jigs fell in popularity. The earliest mention of jigging was by Agricola in his famous 1556 printing of De Re Metallica. He noted that circular sieves were submerged in water while the operator utilized an up and down pumping action to pulse the material through the screen itself. Currently, almost 500 years later this hand jigging method is still employed and is the standard method for most alluvial diamond mining prospecting and final concentrate cleanup in Africa and South America. You can see modern hand jigging machines such as the Bushman Jig or “Diggers Dream” popular in South Africa. Over the past 150 years many variants of the mineral jig were created but it is the author’s opinion that the last 50 years has seen an increase in the actual engineering of highly efficient jigs. Mineral jig principles and theory are widely published in mineral processing journals and throughout the internet so I will not bother discussing the science behind gravity concentration. Excellent information can be found on page 204,
http://books.google.com/booksid=MDiZQCSBENMC&pg=PA204&lpg=PA204&dq=mineral+jigs&source=bl&ots=2KIXnA16k1&sig=hYlf5T8VTtaFNTdRMpynIMukeoU&hl=en&sa=X&ei=pUHwUtijAcbXyAGZz4HABA&ved=0CD4Q6AEwAzgK#v=onepage&q=mineral%20jigs&f=false
What the information lacks is the instruction and knowledge pertaining to the operation of jigs. In the mineral processing world the jig is one of my favorite pieces of recovery equipment. In my operations the combination of jigs and the dredge is a match made in heaven. After WWII jigs fell out of favor (in the metallic mining scene, not gemstones) for the simple reason that flotation techniques were all the rage. It was a simple process with a high recovery ratio. Of course during those years they didn’t know or didn’t care about the harmful chemicals used in the flotation process. After 30 years of stricter environmental laws causing increased awareness and costs in the process, usage of flotation cells sharply declined. Thus, the reemergence of interest in the jig around the 1960’s in places like Malaysia, the Yukon and Brazil. In fact the creation of the circular or round jig for the Malaysian tin fields brought recovery and profit to an all-time high. Every mine operator should love jigs. Why do you ask? Because jigs are user friendly, cheap, environmentally approved and have a recovery of up to 95%. This article deals with the creation and use of mineral jigs for the recovery of diamonds and other gemstones. I thought it would be interesting to show a pictorial timeline of a Pan-American style circular jig being fabricated for the famous alluvial diamond fields in Kono, Sierra Leone. I would like to thank Savana Mining Equipment for sharing their photos.
You can watch the round jig being tested here:
Over the past 40 years my family has used every style of jig imaginable. For diamond recovery we prefer the circular jig over the standard 42x42 square jig. Round jigs sacrifice a tiny bit of throughput compared to the square jig but the recovery factors of the circular jig make up for it. We actually use a combination of both types of jig shapes in some of our operations. The circular jig has also proved an essential design aspect when a jig is needed for mounting on a dredge platform that rides on river current or ocean waves. Over time we have preferred to use a hydraulic action seen here:
For more information on the saw tooth pulse pattern read page 18 here
http://www.conservation.ca.gov/cgs/geologic_resources/gold/Documents/SP87.pdf
I would like to note that the only piece of equipment in my opinion that might rival the jig in alluvial stone recovery is the diamond stir pan popular in South Africa but that’s another article. Please feel free to email with any questions or comments you might have and please, don’t let friends buy Chinese made mining equipment ;)
Wyatt Yeager Msc
wyattyeager@gmail.com
