[Rockhounds] Geology in Progress

[Nathan Martin]

Pete, et al
I did a quick search on "magnetite flotation" and came up with a number of
hits that were suggestive however most of the references did not permit
articles to be downloaded so only brief snippets could be viewed.  Froth
flotation methods were mentioned several times and it makes me wonder if the
natural froth generated by heavy wave action might preferentially bind to
magnetite and enable it to float.  Various polymeric or other chemical
additives also seem to be important in flotation mineral processing
applications.  It makes me wonder what the effect might be of various
impurities in the water near the RI beach that Larry visited.

Isn't it amazing where a simple observation can lead?  I'll bet someone on
the list has some experience in flotation methods and can give us some
insight.

best regards,
Nate Martin
Lexington, MA

On Sun, Jan 4, 2009 at 9:04 PM, R. Peter Richards <rpr at heidelberg.edu>wrote:

> I've seen similar concentrates on Great Lakes beaches, but I don't remember
> ever seeing that the garnet and magnetite were layered, one above the other.
>  In addition to possible grain size differences, is it possible that there
> are differences in affinity for water (hydrophilicity?) that might cause the
> magnetite to tend to float over the garnet, in spite of specific gravity
> differences?  Though I know little about it, differential flotation is a
> feature often used in recovering desired minerals from crushed rock.
>
> Regards,
> Pete Richards
>
>
>
> On Jan 4, 2009, at 5:09 PM, Dennis Buffenmyer wrote:
>
>  Nathan Martin wrote:
>>
>>> Larry,
>>> Seems as if you made good use of one of the few mild days we have had.
>>>  Lets
>>> hope that we get more of that "beach weather" soon!
>>>
>>> One of the things that I find interesting about your observations is that
>>> the magnetite was on top of the garnet. Based on the relative densities
>>> of
>>> magnetite (~5.15 gm/cm^3) and typical New England garnets like almandine
>>> (~4.2 gm/cm^3) or grossular (~3.6 gm/cm^3) , I would have expected just
>>> the
>>> opposite.  I wonder if it is possible that strong wave action could turn
>>> over a density-stratified layer of sand, garnet and magnetite to produce
>>> the
>>> layering that you saw?  I know that bulk granular materials can have some
>>> pretty unusual properties but I don't really know if what you observed is
>>> common.  It may be a really unusual occurrence.  Perhaps someone else on
>>> the
>>> list can comment.  Any sand collectors out there care to venture an
>>> opinion?
>>>
>>>
>>>  Not a sand collector, but could it be a safe venture to make a statement
>> that rocks float?? Most farmers know this and dont realize it.
>> I suspect that it is more likely that the garnet was able to be worn and
>> fragmented to a smaller size than the magnetite and so, the smaller
>> particles sink and the larger particles float. Try it some time on your
>> vibratory lap unit. fill a mason jar full of various size grains/pebbles,
>> chips, and invariably, after a long period of time the big ones,,,,,, wind
>> up on top
>> Dennis Buffenmyer
>>
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>
> ___________________________________
> R. Peter Richards
> rpr at heidelberg.edu
> Morphological crystallographer
>
>
>
>
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