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Identity HelpPlease ID - Chromite? Chromiumite?

9th Apr 2012 06:48 UTCClaire Brimson

Hi

These were found again in Kemi, Finland. Kemi apparently has a Chromium plant/mine area which is outside of Kemi, these were found near the harbour.

Are the crystals Chromite? Why is the rock purple? Streak was blackish.

Also, when white light shines onto it, the purple becomes very strong purple colour. Why is that?

Many thanks

Claire

9th Apr 2012 14:53 UTCRonald John Gyllenhammer Expert

Hi Claire,

I think you're correct about the little black octahedral crystals being Chromite. This looks very much like Chromite ore. I think that the purple colored mineralization may be Chromian Clinochlore like this: http://www.mindat.org/photo-108220.html Good luck with it.

Ron

9th Apr 2012 15:20 UTCAlfredo Petrov Manager

Claire, Check whether the colour looks different under tungsten filament (incandescent) light bulb, and under fluorescent tube lights. That's sometimes interesting for purple minerals coloured by chromium.

10th Apr 2012 20:00 UTCEligiusz Szełęg Expert

looks like chromite with chromian clinochlore (form. kammererite)

11th Apr 2012 11:09 UTCLefteris Rantos Expert

Also keep in mind that much (if not most) "Chromite" is actually not Chromite stricto sensu (i.e. Fe-dominant) but rather the Mg-dominant analogue Magnesiochromite. It is safer to label "Chromite-Magnesiochromite series".

Lefteris.

11th Apr 2012 18:41 UTCClaire Brimson

Many thanks for the information :)

I have doen a bit of 'digging' - http://en.gtk.fi/ExplorationFinland/Moreinfo/kemi.html

Hope you can get into this site - interesting :) The rock is Chromitite

11th Apr 2012 19:39 UTCIlkka Mikkola

Hello Claire

Magnesiochromite has not been found at Kemi. It is chromite (Hytönen, K. Suomen Mineraalit 1999). Chromitite is an error,

it should be chromite ore.

Ilkka

12th Apr 2012 06:06 UTCFranz Bernhard Expert

"Chromitite" is a petrological term / rock name.

"Chromite ore" is a technical / mining term.

Franz Bernhard

13th Apr 2012 05:03 UTCRock Currier Expert

Another reason to get our dictionary of mining, mineral and related terms running.