L David Michaud

About David Michaud

Since 1993, when he obtained his Mining Engineering Degree from Queen’s University, David has acquired experience in operating roles including many years in post-commissioning operations troubleshooting. Mineral Processing and Metallurgy has become a core strength and passion for Mr. Michaud. Learn more at https://www.911metallurgist.com/about-us/

Cave Mining

cave mining (1)In the previous topic, we considered methods of stope mining were the stopes were intended to stay open and collapse and collapse of the roof was not an intended outcome. In some situations however, it may be permissible or even desirable that the roof of the mine collapse to fill the stope as mining proceeds. These methods are called cave mining or caving techniques. Cave mining has the advantage of greater recovery since less of the ore has to be left behind to support the rock above and the resource is not consumed in trying in stabilize the roof. The disadvantages however are; the subsidence occurs in the ground surface above, that progressive collapse may be difficult to control may be unpredictable and hence dangerous and as the roof collapses before or during ore removal, the ore is contaminated with waste which must then be removed. As with stoping, caving is adaptable to both inclined and flat deposits. Let’s start by taking a look at caving in flat deposits through a technique known as long wall mining, commonly used in the mining of coal seams. In long wall mining, flat ….Read more

Witwatersrand Gold Deposits


Here is some history of the Witwatersrand Gold Style Ore Deposits as they related to South Africa since the arrival of the Dutch and the southernmost tip of the continent in 1652. The Dutch set up a small fort where Cape Town stands today and started Market Gardens as a place that the Dutch East India Company ships to shelter and to restock with freshwater and provisions on the long journey between Holland and East Indies. The East Indies was a vital spice trading destination for the Dutch.

As time went on the tiny community expanded and some of the Dutch were allowed to move into the surrounding area to set up new farms on the condition that they still sell their produce to the Dutch East India Company to supply the expanding ship traffic. This arrangement although it was very successful only lasted for a fairly short time before these farmers or Boers as they became known became frustrated by the restrictions set by the company and they started breaking free of the bond and moving inland in their wagons with the Bible in one hand and the rifle in the other.

Towards the end of the ….Read more

Uranium Geology

online-geology-courseI’ll start with a general discussion of uranium its uses, production, resources and the main uranium ore minerals. Then I want to focus the bulk of the course on the types of Uranium Ore deposits, discussing as I go along how those deposit types are formed and how we go about exploring for them. Then I’ll course briefly about how Uranium deposits are mined and how the ore is treated to produce a final saleable product. As usual I’ll end up with a short list of critical take away points.


So let’s starts off with some background to Uranium and the Uranium mining industry. What makes Uranium a particularly economic importance is its radioactivity. Uranium decays through a series of reactions to form a number of new elements:

  • Thorium
  • Radium
  • Radon
  • Polonium
  • Lead

At each of these steps it spins off alpha particles from the nucleus and produces energy. Uranium is not a rare element, it’s found in most rocks although it is more common in felsic rocks like granite than in mafic rocks like gabor.


Granite in general contains about five parts ….Read more

Where to Find Gold

So tonight’s topic of interest is kind of near and dear to me, I’m going to start with the first slide; Rocks and Gold Clues. What rocks tell you about where to find gold, there are clues that they give and those are very important if you’re going to find gold and that’s what we’re here for; right? Hi, I’m Prospector Jess; this is another hangout regarding gold prospecting and how to find gold. I just want to make sure that everybody is in tune with where were going. The adventure for tonight is about rocks and gold and how the two are connected together. I have a background in geology and engineering, primarily from UCSD. I have been an engineering manager for a number of years and then more recently I’ve been doing work helping with gold prospecting. The gold prospecting part I started it as a family adventure but actually it’s deep in my roots, my great-grandfather was a prospector in 1849. So it’s one of those things where I learned about it as a child and then learned again when I had children. And I think it’s important to recognize that a certain amount of excitement and ….Read more

How to Pan Gold

I told you I wanted to do a panning video. So what you’re going to do is, I’m going to break this down a little bit differently. I’m not going to get real scientific on this; I’m just going to put it in plain terminology. Now unfortunately we are probably going to listen to gunshots down the road because its deer season and everyone is getting sighted in. But I am going to show you this, I am going to try and keep it simple but it really is hard to keep panning simple, I am going to warn you about that now. So if you don’t want to watch a pretty in depth panning video, go away, shut this off, and don’t watch it. But I figured I would show you a couple different tricks, I am going to show you some techniques, I am going to show you some things that I like to do. And panning is not something really you can just pick up a book and read on it’s something that comes with practice, so you really need to practice. And of course you can practice with cons.

Now the nice thing about practicing with our ….Read more

Zinc Box Gold Precipitation

The simplest precipitation equipment for a small mine is what is known as a zinc-box (Fig. 150). This consists of a long, narrow, sloping, wood or painted sheet-iron box divided into wide compartments or cells which are separated by baffle-boards and narrow compartments. The bottom of the box slopes to one side to facilitate the clean-up through plug-holes which discharge into a small launder. Near the bottom of each large compartment is a ledge on which is supported a heavy wire screen-tray. These compartments are filled firmly yet are springy with zinc shavings or filament. The gold- and silver-bearing solution is turned into the first narrow compartment, and the baffle, which does not reach the bottom, deflects the solution under the tray holding the zinc. The solution flows upward through the zinc, over the side of the compartment, down by the next baffle to the next lot of zinc, and so on, through 6 to 10 cells to the discharge, whence the solution flows to a sump or storage-tank. At this point it should be practically barren of precious metals. One cubic foot of filament will serve 6 to 10 tons of solution a day.

From time to time during a ….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

Mining Tailings Pumps

The disposal of mill residues or tailings costs 2 to 6 cents pel ton, however carefully it is done. Residues may be moist sand which can be conveyed by belt or trucked to a dump, moist solid slime which can be handled somewhat similarly, or pulp which can be pumped to a suitable place. The handling of sand and slime does not call for any special comment. With rails, a dump

mineral processing centrifugal pump

may be extended outward or it may be circular, the latter method being preferable. Pumps suitable for pulp have already been described. Pulp should be dammed in a dump made of the drained material. As the solids settle (a little lime or cement added to the pulp helps) and more or less clear water flows to one point for discharge to waste or for re-use in the mill, walls of the slime are built up with a good batter. If they are too steep, they might collapse. On some well-made dumps, every shovelful of slime can be seen up the side of the walls. The author has seen such dumps containing 10,000 to 2 million tons.

A tailings pile should ….Read more

Magnetic Black Sand Separator

During the past 50 years or more there has been a great waste of money, energy, and time in devising, building, and trying many machines to recover gold and platinum, also gemstones, from black sand. Volumes have been written on the subject, and many inquiries have been made by prospectors and others who thought that although they could not save the precious metals, which most likely were never there, some process must be suitable. Near Nome, Alaska, the black sand was rich, and some on the west coast of the South Island of New Zealand is being worked at a profit at the present time. A few spots along the California- Oregon coast were worth handling, as have several along the rivers in the western United States and Canada. The black sands from sluicing and dredging operations are worth careful treatment because they are from the concentration of thousands of yards of gravel daily. By-product black sand from inland placering is often richer than beach sand. But generally, black sand, unless a concentrate, is not worth much effort. In any case, it is worth spending a dollar or two to have an assay made for gold of a carefully taken ….Read more

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