Gravity Concentration

Falcon Enhanced Gravity Separator

Enhanced gravity separation devices (centrifuges) have been patented for over a century but were impractical until recently. The physical laws behind the concept were well understood but engineering had to catch up with the science. This included the development of abrasion resistant materials, the improved design of rotating equipment that allowed higher RPM, and a good understanding of slurry flow, rheology, and the effects of particle shape. Only in the last decade has engineering entered the dawn of enhanced gravity separation. The more we learn, the more we realize how little we know. A parallel can be found in the history of the hydrocyclone which, although in widespread use for decades, experienced an upsurge of study and improvement after 1960 and which continues to receive attention in the literature. Mineral processing technology has advanced across the boards recently and enhanced gravity separation has been part of this evolution. A few things are now known with some certainty.


While units have previously been defined by diameter, capacity is more a function of surface area. Two units of close diameter must be assessed by rotor surface for comparison. Within the Falcon SB product line from 104 to 965 mm (4” to 38”) diameter, ….Read more

Mercury Amalgamation

Mercury or quicksilver fed into stamp mortar-boxes and riffles or applied to copper plates has been for ages the method of catching free gold. Many millions of ounces of gold have been saved thereby, and the mercury has been returned to circulation with small loss. Amalgamation is still practiced, but the recovery of gold by traps, jigs, cells, and cloth is lessening the amount so saved, although gold from these appliances is amalgamated for cleaning up.

Amalgamation is affected more or less by some pyrite minerals, especially if decomposed, also by antimony, bismuth, and copper.

If such is the case, tabling could precede amalgamation or corduroy should be substituted.

Mortar-box. If a mine has a stamp-mill and inside amalgamation is desirable, mercury is added to the mortar-box in quantity enough to form a spongy amalgam therein and not enough to work out on to the copper plates and make them sloppy with mercury.

mineral processing hydraulic gold trap

Copper Plates. Pure copper, 7/64 inch thick, is rolled into plates or sheets for the amalgamation of gold; 2 to 4 square feet is used per ton of ore per day. New or used plates are procurable, but care should ….Read more

Cheap Sluice Mat – Corduroy

Cheap Sluice Mat

Details of the use of corduroy are given in the section covering gold and silver, but there is no reason why this material should not be used by the small miner in the concentration of any sulphide ore—silver, mercury, copper, lead, antimony, and sphalerite, for example. Corduroy forms part of the concentrating equipment of the platinum ores of Transvaal, South Africa, whose value occurs

cheap sluice mat

Fig. 125A.—Top and end views of corduroy. It should be laid with the high side facing the flow of pulp. Gold and sulphides are caught in the furrows between the ribs.

in the metallic state in the oxidized zone and as sulphide at depth. At a small mine in the development or even the regular production stage, corduroy could form a temporary means of saving sulphides until the mill is enlarged and other suitable concentrators are installed—jigs, tables, or flotation cells. A high recovery could not be expected, but average results should be satisfactory; the expense of building sloping tables for the corduroy and their operation would be low. Experience with an ore and the ….Read more

Gold Planning

I have been given the opportunity to maybe teach you guys how to pan some gold and find some gold. I’ve been prospecting, my family been prospecting for many years. So we have a good mine just up the road. And hopefully today we can go out and find a little bit of Gold and anybody can go out and find with just a gold pan. That’s my goal just to find some gold, get it in the pan and show you guys what to do so let’s have some fun.

We’ve got a stream here and we know it’s a gold bearing stream we are in an area that’s produced a lot of gold, so nobody has mined in this section right here so today I want to go up and check out different elevations and see what we can find for finding some gold lets have some fun.

As you can see I’m not going to dig right off, right at the bottom of the stream bed. We’ve got this hill that’s sloped off here and its showing me gravel from when the stream used to be up there. It may have been hundreds of thousands of years ago that ….Read more

Gravity Concentrators & Jigs Compared

A Gravity Concentrator has the bed fluidized 100% of the time.A Jig is fluidized only 50% of the time.
A Gravity Concentrator works at 150 g forces.A Jig works at 1 g.
Material is caused to move in a lateral movement through the Gravity Concentrator.A Jig has a lateral movement and a vertical movement.
The Gravity Concentrator moves concentrate laterally at very near the speed of the cone and at the same time it moves the gangue being treated in a lateral vertical plane across the concentrate face.A Jig moves concentrate down into the hutch and gangue horizontally across the bed.
Gangue in the Gravity Concentrator picks up speed as it travels through the unit and the more centrifugal speed it picks up the closer it gets to the speed of the Gravity Concentrator.Materiel in a jig also picks up speed horizontally but as it does so it moves away from the speed of the jig which is zero and the faster it goes the less chance there is for concentration.

Flour Gold Recovery

Flour Gold Recovery Fine Gold Recovery Equipment

Flour gold can be defined as ultra-fine gold found in a low micron size fraction, often smaller than 74 microns or 200 mesh.  Reality is that with today’s fine gold recovery equipment, this is a low ways away from the elusive microscopic gold small prospectors want to know how to recover.   Falcon’s iCon gravity concentrator, in conjunction with a conventional shaking table, can recover in excess of 85% of GRG gold. A screen analysis of the gold particles has show test samples with as much as 44% of the gold in the -74 microns (-200 mesh) size range.  High metallurgical efficiencies of concentration within the size ranges of 1.5 mm (-10 mesh) to about 37 microns (-400 mesh) allows recoveries of trace quantities of contained high specific-gravity minerals from what would otherwise be “plant tailings”.

The iCon i150 and i350 are, for a small miner, high capacity gravity concentrator designed for feed throughputs of 1 to 15 TPH, for feed material finer than 2 mm (-10 mesh) in size. The high-G cones operate at feed pulp densities of 60% to 65% solids (by weight) and ….Read more

Diamond Dredge

With regards to diamond dredges and dredging, the kings of the 1970s were Consolidated Diamond Mines and Marine Diamond Corp. both parts of the famous DeBeers company, control the coast of the Namib Desert and the waters and more important, the ocean floor and beaches of this treasure cheat of gems. So rich were the original finds that diamonds could be picked up in scene areas without any digging whatsoever.

diamond dredge

That was in 1908 when the desert and the treacherous coast were the only guardians of this newly discovered wealth. The desert is still almost impassable, and the rough seas off a coast almost without harbors are more than fortune seekers can face. In recent years desert patrols and other security measures have further isolated this already inaccessible area.

By now the day had cleared. In place of the overcast, the sun shone fiercely through the plane’s canopy, while down below a heavy fog rolled in from the sea. So thick was the fog, as we came in to land on the salt pan which served the camp at Hottentot’s Bay as a landing strip, that I could see no ….Read more

Understanding the Gold Centrifuge by Comparing it with a Sluice Box

Centrifugal separation of gold experienced a regain in activity with the advent of the Knelson Bowl. This device appears extremely efficient in recovering fine gold, although very little published data are available.

Installing a gravity plant increased overall gold recovery by about 3-4% in some plants. Gravity concentration was achieved with pinched sluices and 76cm Knelson bowls, with a significant increase in fine gold recovery.

Again, the first material in fills the rings completely. At this point any similarity in the two centrifugal type concentrators begin to separate as the unit greatly enhances and improves the centrifugal factors.

  1. A 30 inch Knelson Concentrator spins at approximately 400 RPM
  2. creates 60 forces of gravity,
  3. does not allow compaction,
  4. will process up to 40 tph of minus ¼ inch material,
  5. in typical alluvial operations will operate up to 24 hours without clean up with no increased loss of gold.

In order to understand what happens with a particle we must return to the sluice box for a moment. We realize that as the material heads down a sluice box it picks up speed. In fact, in a rough box, it will get up to nearly 30 mph. The closer it gets to full speed ….Read more

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