mining and mineral thread

What you are doing is very important in the dry food, pharmaceutical and laundry detergent industries. The difficulty may be getting them to reveal their methods.

Another way to separate by size for analysis is by settling time in a viscous liquid like olive oil. Diamond dust is separated by size for lapping that way, and a topsoil sample from sand.

Hi there

Thanks for affirming words.

Separation by falling through fluid column

- on a trivial level there is a "cheat" (it isn't actually) you can do when manually wet sieving.

Because the sieve "blinds" with just above sieve sze particles - makes it a lot quicker to deal with those last. If you stir you sample mix in the water, if you leave it for a few seconds, if you ladle from near the surface you will catch only fines, which will drop straight through the sieve. You can ladle into the sieve shorter and shorter times after stirring, to get coarser and courser particles. Finally you have the larger "drops straight to the bottom" sizes - with no "clay" and/or other fines - so the tendency to bind on/in the sieve is much much less. Hence "blinding" of the sieve only happens at the end, and then with nothing left to bind thus reducing the tendency to "blind".

That was a point my not-notably-talkative contact nodded about with a general "you are well on the way" body-language.

This si the "air-elutriation" idea as best as can ASCII-sketch

^ ^ air-flow ^ \ \ / / \ \ / / \ \ / / \ \ / / ^ ^ air-flow ^

That is how goose down is separated into grades for high performance winter outerwear.

I had learned to join thin polyethylene sheets on a hot light bulb to make hot air and hydrogen balloons and UFOs that I and others flew over Exeter NH. I had no part in the famous one though I had made smaller hot air models of tissue paper with flame coloring such as road flare contents. A few cells taken from a 9V battery could briefly power blinking Christmas bulbs. The instructions and patterns for balloon panels (gores) had been printed in Boy's Life magazine. At low angles the otherwise nearly invisible clear plastic reflected the sun and clouds like calm water or a windshield and may have looked like a shiny flying saucer. The most saucer-like for their flat tops were dry cleaners bag parachutes with minimal ballast that rose on warm moist thermals from our field.

One evening I saw someone else's UFO drifting past the stars, like but not quite right for a plane, more a candle. I triangulated its altitude by pacing perpendicular to its path until it was at 45 degrees, it was only 100 feet up. Just looking at it without a reference it could have been at any distance and size.

Eyewitness testimony on TWA 800 shows how the eye misjudges the unfamiliar. The reported antiaircraft missiles were actually the flaming fuselage after the center fuel tank exploded and blew off the front end, unbalancing the rest into a steep climb.

Thanks for this idea for recovery of the "dust" which is actually part of the sample.

Yes, take what wins you can as soon as you can. You remind me of these "cyclone" machines in woodworking shops.

The "very very fines" which form a "smoke" are unlikely to contain values? Which would be denser and be cycloned-out into another fraction? So if the "normal density" "very very fines" end up in a filter whose "with dust weight" - "original weight" is taken to be the mass of those very very fines, that would work. Unlikely to need to recover them.

I will look into this. I can start with using a "wet&dry" workshop vac. to start "concept" experiments. Mine you can connect the hose to the "blow" side, which should help.

Thanks for this idea for recovery of the "dust" which is actually part of the sample. ... The "very very fines" which form a "smoke" are unlikely to contain values? Which would be denser and be cycloned-out into another fraction? So if the "normal density" "very very fines" end up in a filter whose "with dust weight" - "original weight" is taken to be the mass of those very very fines, that would work. Unlikely to need to recover them. ...

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In chemistry practice such filtrates are collected on filter paper which is either very low ash when burned, or the ash weight percentage has been measured. The paper and filtrate is burned out in a previously weighed crucible and the crucible and residue weighed without trying to scrape it out. The residue can be analyzed to see if it contains metals, perhaps with the blowpipe and charcoal.

I will look into this. I can start with using a "wet&dry" workshop vac. to start "concept" experiments. Mine you can connect the hose to the "blow" side, which should help.

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You can measure the pressure rise or drop related to air flow with a clear tube containing colored water. If sloped at six degrees the height of water is amplified 10x. As long as your setup gives repeatable numbers it needn't be accurate, you can compare readings to results.

I know YOU want the fines which hopefully a cyclonic filter can capture a signifcant portion of, but everyone else wants the final exhaust air to be dust free, especially free of those pesky sub-PM10 particles which don't play nice with lungs. I thought a cyclonic filter might be a win-win :-). If crude sieving is useful and you build it yourself you could have two stages of cyclones, the first a "bad" one to only get the big chunks, then a "good" one to get the mid-range down to some target fine size, and then a normal flow-through paper air filter element to get the really fine stuff before exhausting the air.

There are lots of plans and videos online to build your own to go on top of a 5 gallon bucket, along with molded plastic models.

I must misunderstand. I thought sieving was just for grading by size. Having done a little placer mining I can well understand why once you start processing wet you need to keep processing wet. Even a long period of time may not be adequate to dry material in a high humidity environment.

As defined, not exactly. I have used a dry washer, which is functionally a course sieve followed by a "sluice" using air and vibration as the means to keep material moving instead of water. Since our only net desired material was gold I noticed that there was less ultra fine "flour" gold in material handled by dry washer as opposed to material run through a proper sluice with water. In either case obvious nuggets were picked out, and final processing was wet panned by hand, where small and tiny nuggets were picked out, and then finally that run through a spiral concentrater if panning indicate enough fines to be worth the effort.

I've seen a few things used for ridges on dry washer separators. Expanded metal which I didn't think worked very well was one. Another was catch angle pieces of metal straight across the bed resting on what looked like a course cordura mat that was easily permeable to air. The bars where typically part of an assembly, that was hinged on pins at one end to allow for easy clearing of captures into a container. When hinged down it pinch the mat or carpet material. I've seen similar mat material used behind the same catch angle metal bars on wet sluices.

Thanks

Thanks everyone. Good ideas here, and concepts opened-up here.