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Improving Mindat.org"Evansite" caption

2nd Oct 2006 06:02 UTCAlan Plante

Photo number 59495 popped up on the main page with the caption "Evansite." No where in the information presented with the photo does it say that this is - I believe - a discredited name(?) or - at best - a dubious species... (I don't think there is even any crystallographic data available on it. Dana 8th just notes: "Possibly amorphous.") I didn't check the mineral page for it, but whatever may be there doesn't help if there isn't some way to make sure captions present the uncertainty.

(Another little problem with getting people good information... :~{ )

Alan

2nd Oct 2006 12:06 UTCAlfredo Petrov Manager

It's just as much a mineral as any other generally accepted amorphous species (i believe).

2nd Oct 2006 12:48 UTCJim Ferraiolo

It's still considered valid, though it shows a similarity to bolivarite.

The last paper done on evansite, Garcia-Guinea et al.

, in the conclusions state "their chemical compositions are sufficiently dissimilar to preclude them from being the same mineral species if they had been well crystallized."

2nd Oct 2006 15:41 UTCAlan Plante

Okay, so it hasn't been discredited - but nor has it been validated? Still dubious?

My understanding is that acceptance of an amorphous species these days requires quite a bit of jumping through hoops to prove they are not mixtures of some sort. So unless those hoops have been jumped through, I think the question mark has to remain after the species' name.

Alan

2nd Oct 2006 16:35 UTCAlfredo Petrov Manager

Evansite was discovered several decades before bolivarite, so evansite would have priority, if it were ever determined that they were the same.

3rd Oct 2006 01:22 UTCJim Ferraiolo

Alan,

They both appear to be valid, but whether or not they're the same mineral is the question. I can send you the 1995 article, if you're interested. Both obviously predate the IMA - bolivarite in 1921 and evansite in 1864.