In this Astronomy Now article, "Should Mars really be black?", scientists claim to have produced red hematite from black magnetite without the presence of water through a purely mechanical process.

 

http://www.astronomynow.com/news/n0909/18mars/

 

“Subsequent analysis of the flask material and dust has shown that the magnetite was transformed into the red mineral hematite, through a completely mechanical process without the presence of water at any stage of this process.”

 

My question is: Can magnetite Fe3O4 really be transformed into hematite Fe2O3 through a purely mechanical process? Magnetite consists of a mixture of iron(II) and iron(III), and hematite is just iron(III), so somehow there's a room-temperature redox process going on?!?

 

As a side-note I live close to a very windy (mechanically active) area where there is much magnetite in the beach sand. Still, no hematite whatsoever is present in the ground.

 

Cheers,

Mike

wasn't there a thread on this recently?

 

as i said in the other one, it cannot happen without a source of oxygen.

 

it is possible to make many reactions happen by mechanical agitation, exapmples include shock sensitive explosives, whisking eggs to break appart the protein etc.

 

there is nothing wrong with that part.

 

but Fe2O3 has a higher fraction of oxygen than Fe3O4. this oxygen cannot appear out of nowhere unless you are depositing a chemical with a high fraction of iron. the article doesn't state whether this is happening or not.

wasn't there a thread on this recently?

 

Well, yes. I just considered it more appropriate to post it under inorganic chemistry than under astronomy.