[Rockhounds] Elutriation

Wed Jan 7 17:28:00 PST 2009

Jay,

You are correct that the grit breaks down to finer grits during use. 
Recycling three tumbler loads of coarse grit (60-80) might give me two 
loads of finer grit (120-220) and part of a load of fine stuff 
(320-600). The advantage is that I usually only need to purchase coarse 
grit.

But recycling with a single stage elutriator is somewhat of a pain. I 
usually dump the grit at the end of a tumbling stage into a big bucket 
and have a recycle party when it gets full. I don't do all that much 
tumbling anymore, so it takes me a few years to fill the recycle bucket.

Kreigh

On Wednesday, Jan 7, 2009, at 14:45 America/Detroit, Jay Bates wrote:

> Kreigh,
>
> I know you have tried elutriation to separate grit from rock dust 
> resulting from using using the grit to grind down rocks. I am 
> wondering if you obtained any useful grit as I know grit breaks down 
> into smaller sizes with use. I use 60/90 grit continuously to  make 
> spheres. Some  people seem to think they can reuse the grit after they 
> separate it from the rock dust. I maintain that you can recover the 
> grit but it is of a smaller size and not much use in sphere grinding.
>
> pmodreski at aol.com wrote:
>> Kreigh & Jim, & the List,
>>
>> Just wanted to say, I tried searching on our USGS website to see if I 
>> could locate a report or paper on this, but have not had any luck.  I 
>> also tried looking in the older, printed volumes we have listing and 
>> giving subject indices to USGS published reports (I thought the 
>> old-style printed index might find it for me, when the online 
>> searching failed), one volume for pre-1962 and one for 1962-1970, but 
>> I don't see anything resembling what you are looking for.
>>
>> I would think that this technique,  requiring seperatory funnels & 
>> U-tubes with stopcocks (not that you couldn't improvise with simpler 
>> equipment), might work for relatively small quantity samples of 
>> mineral grains, but might not be too workable for separating large 
>> quantities of material (of silicon carbide grit, such as Kreigh is 
>> talking about), as it would be likely to clog the tubes or valves.
>>
>> Pete
>>
>>
>>
>> -----Original Message-----
>> From: Kreigh Tomaszewski <Kreigh at tomaszewski.net>
>> To: Rockhounds at drizzle.com: A mailing list for rock and gem 
>> collectors <rockhounds at lists.drizzle.com>
>> Sent: Tue, 6 Jan 2009 9:34 pm
>> Subject: Re: [Rockhounds] Elutriation
>>
>>
>> Jim,  Your description was clear enough I'm sure I could build 
>> something that worked, but I would still like to see the paper as I 
>> am sure it would save me a lot of time experimenting to make things 
>> work right.  Kreigh
>>
>> On Tuesday, Jan 6, 2009, at 22:35 America/Detroit, Jim Murowchick 
>> wrote:
>>> Hi Kreigh.  I'm still looking for the paper--it's one of those that 
>>> I keep >
>> finding
>>> when I don't need it, but when I want it, I can't remember where I >
>> stashed
>>> it. I can probably draw a sketch of the system, though, if I can't >
>> find the
>>> paper. I'll look for it for a few more days, then I'll make a 
>>> sketch.  I was going to make the system a few years ago, but found I 
>>> didn't >
>> need it.
>>> Now, I have a student looking at soils in the Bahamas, and we might >
>> start
>>> separating out the very fine materials to determine the source of 
>>> the airborne dust components. I think the elutriation system might 
>>> be >
>> modified
>>> to make that separation.  Jim   On 1/6/09 9:29 PM, "Kreigh 
>>> Tomaszewski" <Kreigh at Tomaszewski.net>
>> wrote:
>>>
>>>> Jim.  That is pretty cool. I use a single stage to recycle tumbling 
>>>> grit
>> and
>>>> have to make multiple passes with decreasing water flow. I would
>> like
>>>> to see the paper. Being able to separate multiple grit sizes in a 
>>>> single pass would save me a lot of time.  Kreigh   On Tuesday, Jan 
>>>> 6, 2009, at 12:40 America/Detroit, Jim Murowchick >>
>> wrote:
>>>>
>>>>> For anyon
>> e interested, there was a USGS paper, probably from the
>>>>> 1960's, that described an elutriation system for mineral 
>>>>> separation. It consisted of a series of tall (10-15"?) U-shaped 
>>>>> glass tubes (oriented vertically), each with a stopcock at the 
>>>>> bottom of the U. Each glass tube had a smaller inside diameter 
>>>>> than the one upstream, and they were connected in series with a 
>>>>> rubber tube. At the start, a separatory funnel with a >>>
>> stopcock
>>>>> at the bottom held water, and was at the highest elevation. At the 
>>>>> outflow end, a rubber tube from the last U drained into a 
>>>>> collection flask.  With a slow stream of water flowing through the 
>>>>> system (feeding into the separatory funnel, a slurry containing 
>>>>> the sample was drizzled into the separatory funnel. The heavies 
>>>>> collected at the bottom of the first U, lighter minerals moved on 
>>>>> to the second or third U, and the
>> lightest
>>>>> ended up in the collection flask at the end. Fine-tuning of the 
>>>>> water
>> flow
>>>>> and gradient controlled the separation efficiency, and the 
>>>>> separates
>> were
>>>>> then emptied through the stopcock at the bottom of each U tube.  
>>>>> I'll try to find the paper, in case anyone wants the specifics, 
>>>>> but if anyone
>> can provide the reference info, I'd appreciate it.
>>>>>  Jim Murowchick
>>
>
> -- 
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