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Micro ID HELP - red crystal

Posted by Roger Curry  
Roger Curry September 16, 2014 12:34PM

Size - approx 0.2mm
Shape - thin tabular hexagonal
Colour - bright red
Lustre - metallic
Transparency - opaque
Magnetism - non-magnetic
Location - Coldberry Gutter, Teesdale, UK
Outcrop rock - ironstone nodule from namurian shales
Associated minerals - quartz, kaolinite, millerite

Any ideas or suggestions for ID would be gratefully recieved. My guess and Steve Garza's can be found on this Mindat thread

open | download - pyrrhotite1.jpg (6.7 KB)
Holger Hartmaier September 16, 2014 02:46PM
How about vanadinite? It can occur in short hexagonal prisms.
Roger Curry September 16, 2014 03:57PM
Hi Holger,
I think vanadinite would be transparent at the extreme thinness of the crystal, also the lustre is wrong - this tiny crystal reflects light like glitter.
Henry Barwood September 16, 2014 05:01PM
Hematite pseudomorph after pyrrhotite/smythite?

Henry Barwood
Troy University
Troy, Alabama USA
Spencer Ivan Mather September 16, 2014 06:23PM
I was also thinking Hematite...
Roger Curry September 16, 2014 11:57PM
So how do I determine whether this is an oxide or a sulphide? It's too small for wet analysis.
Holger Hartmaier September 17, 2014 02:05AM
Would immersing the crystal in various kinds of fluids of known density, such as used in gemology work? At least you could obtain a specific gravity. Also, I wanted to ask if the "glittery" reflections you described were due to surfaces on the crystal itself or due to some secondary mineral coating.
Roger Curry September 17, 2014 10:28AM
Good suggestion Holger, unfortunately I haven't the facilities for either density measurement or any further microscopy - better photos would help. I think perhaps I will try to get someone interested in my nearest university. Would a scanning electron microscope be the best route? Perhaps the X-ray analysis from the 'scope be able to nail down what this is.
Does anyone have a suggestion about who to approach at Durham University? Perhaps someone in the Dept of Earth Sciences will be into local minerals enough get some images and qualitative analysis. I can't go the commercial route.
Roger Curry September 18, 2014 08:15PM
Hi all, mystery "crystal" ID!
See the companion thread
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