[Rockhounds] Mining Lake Michigan Sand for Magnetite

[Rik Dillen]

And what is perhaps a very important argument against mining magnetite sands
: magnetite is not the type of iron ore that most steel companies like. The
reducibility in hot furnace circumstances is less good than that of
hematite, even taken into account that one of the three Fe-atoms in
magnetite (Fe3O4) is already reduced to the bivalent state), and that pure
magnetite contains more Fe (about 72.5 %) than hematite (70 %). That less
good reducibility has to do with kinetics, specific surface / porosity at
high temperature. Magnetite contains also mostly quite high amounts of
sulfur (as sulfides) and phosphor (as phosphates). This last point is e.g.
the case in iron ores from northern Sweden/Norway (Kiruna & Gellivare).
Those elements are the nightmare of any steel factory.
So I doubt for those reasons that it would be profitable to mine magnetite
in such circumstances as an iron ore.
Grts,

Rik DILLEN 
E-mail rik.dillen at skynet.be 
Homepage : http://users.skynet.be/rik.dillen 

MINERANT 2009
9-10/5/2009
Antwerp Expo - Antwerpen - Belgium
www.minerant.org

-----Original Message-----
From: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of jb
Sent: vrijdag 20 maart 2009 6:50
To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
Subject: Re: [Rockhounds] Mining Lake Michigan Sand for Magnetite

Kreigh Tomaszewski wrote:
> I got a request from another List I am on for a sample of Lake 
> Michigan beach sand that contains Magnetite. It got me wondering.
>
> Has anyone heard of mining (Lake Michigan) sand with a magnet to 
> extract the magnetite at a commercial scale? They do it commercially 
> with Taconite, and they make their own sand by crushing rock, all for 
> about 3%. I have filled more than a dozen film cans with magnetite 
> using a super-magnet on about a hundred square feet of (Lake Michigan) 
> beach sand.
>
> Is the percentage of magnetite sufficient to make such an operation 
> profitable? A crane with an electromagnet on a barge just offshore 
> could process a lot of sand as it circled the shores of the Great 
> Lakes with minimal economic impact.
>
>
....
> Kreigh
>

Probably not; you can be sure that the mining companies have thought 
about it also.
Most of the black sands have minor magnetite percentages. Some have 
enough ilmenite and/or  rutile in them to make them worthwhile as an ore 
of titanum and are processed for that; in fact ilmenite is much more 
common than magnetite or hematite in the sands. Even so, placer deposits 
are mined much more than beach sands. (I guess it's more convenient to 
have an ore body in place than one that is constantly being shifted 
around. :) .)
Garnets, chlorites, and heavy dark silicates are usually the other main 
constituents, the usual products of erosion of mafic rock.
john