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Identity HelpUnknown mineral from the Sakavalana Mine, Madagascar

22nd Jan 2020 22:48 UTCChris Emproto

Associated with pezzottaite and albite. Can't fit it the sample in the SEM to analyze it. Anyone have any ideas? I'm thinking hambergite.

22nd Jan 2020 23:28 UTCRuss Rizzo Expert

Christopher,

My eyes aren't as good as they used to be, and the photo is a little fuzzy when enlarged. I'm thinking bavenite.

22nd Jan 2020 23:51 UTCChris Emproto

The field of view is ~1.0mm. I was between bavenite and hambergite from the locality's mineral list, but my only reservation was that the terminations aren't as squarish as most of the bavenite I've seen. They look sort-of uneven and are dull (so hard to see faces), but they're so tiny it's really hard to tell.

23rd Jan 2020 02:01 UTCRuss Rizzo Expert

Hambergite would be a close second. Like you say, its so hard to make out the crystal faces.

23rd Jan 2020 02:27 UTCPaul Brandes 🌟 Manager

Is there any way you can sacrifice a small sample of the unknown to have it analyzed?

25th Jan 2020 19:27 UTCChris Emproto

I'll probably just try Raman if I can get permission to use the instrument. I'm not opposed to sampling nice crystals, but these are so tiny and fragile that I fear if I try to knock one off I'll end up wrecking the whole thing. The entire cluster is only ~300um across, and I'm no brain surgeon.

23rd Jan 2020 02:55 UTCMichael Hatskel

Christopher Emproto ✉️

Sakavalana Mine

Judging from the crystals along the periphery of the cluster:

1. they look like 6-sided prisms but terminations don't look like quartz;

2. they have more body (thickness) than bavenite blades would have.

I would say hambergite looks more plausible.

23rd Jan 2020 03:04 UTCFrank K. Mazdab 🌟 Manager

looks like you need a bigger SEM... lol.

And if the crystals are hambergite, the EDS spectrum might look pretty boring anyway... depending on the generation and quality of your detector, there may be essentially no peaks to see. Though that may itself give you the answer you seek...

25th Jan 2020 19:23 UTCChris Emproto

The whole sample itself is ~5cm tall, so it would run into the lowermost condenser lens of our instrument. The crystals are also well tucked away, so the signal would already be very poor and diluted by albite and whatever the tan clayey material is. I checked it all around and this is the only cluster.

25th Jan 2020 21:11 UTCUwe Kolitsch Manager

With an acupuncture needle coated with a tiny bit of grease (skin or other), one crystal could be easily removed and then used for Raman and/or SXRD.

25th Jan 2020 23:20 UTCChris Emproto

That sounds like a good idea, I will try that.

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