FMF - Friends of Minerals Forum, discussion and message board

[Jim Prentiss]

Hi Everyone,

Has anyone out there seen that Chinese Limonite that was availible a few years back that was so bright and shiny?

My question is about the luster. Is it real or altered? Did the folks actually dig it up that way or not?

Secondly, it is Limonite or Goethite?

Thanks.

Jimp

[Peter Megaw]

Tecnically there is no such thing as limonite...it's a garbagecan term for a mixture of iron oxides and hydroxides. Much of what looks like this is mostly goethite and yes the luster is natural. When it gets this kind of irridescence it is often called "turgite" which is supposed to indicate a tiny copper content...but almost no-one except exploration geologists care and they'll put a drop of hydrochloric acid on the stuff and scootch it around with a steel needle or pin to see if copper plates out.

The stuff can be pretty!

[Jordi Fabre]

It is Goethite, and yes it could be so bright. In Rio Tinto Mines, Spain, few years ago appeared so brilliant and still more colorful. I don't mean that the Chinese ones have a real or altered luster, just that this luster could be natural.

[alfredo]

Goethite is one of the several types of "limonite" so, yes, it can easily be both goethite and limonite at the same time. Goethite is the most common species of limonite.

Botryoidal goethite with iridescent surface colors is not uncommon around the world, although your piece is an unusually good representative. I see no reason to think it's been artificially enhanced, just well cleaned (Is that an enhancement?), although I can't swear someone hasn't found a way to enhance iridescence.

[Jim Prentiss]

Thanks Guys,

That is what I was hoping.

jimp