[Rockhounds] Geology in Progress

[R. Peter Richards]

Clearly it's due to polluted water.  Quick, somebody call EPA!!! Or not.

Pete Richards


On Jan 4, 2009, at 9:42 PM, Nathan Martin wrote:

> 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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___________________________________
R. Peter Richards
rpr at heidelberg.edu
Morphological crystallographer





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