FMF - Friends of Minerals Forum, discussion and message board

[John Nash]

I would appreciate any opinions regarding what the orange, tabular crystals in this natrolite specimen from South Island, New Zealand might be. I've attached a picture of the full specimen, then a couple close-ups. The last one is a bit grainy, I fear, its at the very limit of my macro lens, with a FOV of about 1 cm.

Thanks,

John

[chris]

Hi John,

Assuming this specimen comes from Hokonui Hills, it might be Heulandite. I found a photo on Mindat with crystals having about the same habit here : https://www.mindat.org/photo-6573.html

However, note I'm not an expert of this mineralogy, so take my guess with caution.

Chris

[crocoite]

The crystals look a bit "thin" for heulandite for me. Maybe Baryte?

[John Nash]

[Jordi Fabre]

Baryte don't match very well with Zeolites deposits. Why don't you try if by chance it fizz with HCl/vinegar? Calcite has hundreds of different crystal forms and it match well with Zeolites...

[crocoite]

I beg to differ Jordi. Down our way, Baryte is commonly associated with zeolites.

[Jordi Fabre]

[crocoite]

No problem Jordi.

Here are a couple of examples, one from New Zealand, one from Australia. Sorry, these are old photos. I need to retake at some point in time.

[Pete Modreski]

A neat looking specimen! (the natrolite). I would also have offered that "I'm not familiar with Baryte associated with zeolites"--out "our way" (western U.S.) I can't think of where they are commonly found together. But I guess things can be different, down south there! I've been puzzling over what other crystal they might be--something (apparently) orthorhombic, transparent, this amber color. Baryte certainly sounds likely. As was said--good to confirm that it doesn't fizz.

[John Nash]

Thanks all for your comments! I just tested the material and it does not fizz in HCl. I also just realized I've got large tabular crystals of Baryte from Morocco that appear identical to these tiny ones (attached). So Baryte is a good guess?

John

[John Medici]

Baryte is my guess. Crystal form and phantom tendency are right for Baryte, although I don't remember much Baryte associated with eastern USA zeolites. Interesting combination!

[Tom Tucker]

Micro Baryte crystals are not uncommon with the zeolites, including analcime, chabazite, mesolite and harmotome, in the basalt at Sugar Grove, West Virginia

[John Nash]

Thanks again for the opinions. I've contacted Frank van Betuw of the Otago Rock and Mineral club in Dunedin, South Island, New Zealand, who has passed the photos and explanation on to some local zeolite experts. What a remarkable thing, this internet. If this is the sort of stuff they find there it looks like a trip to New Zealand will be necessary! I should hear in a week what they think of it and where it probably came from, hopefully a specific locality. I'll post a note when I hear from them.

John