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Identity HelpEpidote from Elba

13th Apr 2018 15:54 UTCJoshua Chambers

Hi all

I've got another specimen with a slightly vague locality. After looking at epidote from Elba on mindat, I have noticed the similarity to hedenbergite from Torre di Rio (https://www.mindat.org/loc-2153.html). I am aware of the difficulties when it comes to differentiating pyroxenes from one another, could it be hedenbergite?

Apologies for photo quality

13th Apr 2018 15:58 UTCJoshua Chambers

Here are some close ups. FOV= roughly 4mm. Silky lustre, with some crystals looking possibly fibrous where fractured.

There is another mineral present on the specimen. Looks to be rhombohedral in shape around specimen, calcite? Or possibly some sort of zeolite, stilbite for example?

Any help is appreciated

Thanks in advance

Josh

13th Apr 2018 16:37 UTCScott Rider

It does look like hedenburgite, but like you stated above pyroxenes are hard to identify. You'll probably have to have it analyzed to be for sure.

The last image is probably adularia. The rhombic shape and the striations on the surface sure looks like whats typical of adularia.

13th Apr 2018 17:08 UTCPavel Kartashov Manager

This is rather actinolite than any pyroxene or epidote.

13th Apr 2018 17:17 UTCScott Rider

Pavel, I was thinking that as well. I recently dug at Calumet mine in Colorado, that is known for its "uralite" specimens, basically actinolite psuedomorphs of a pyroxene mineral (people say diospide). These sure resemble some of the specimens I found, having the fibers assembling in the shape of another mineral.

13th Apr 2018 17:23 UTCGregg Little 🌟

With the fibrous habit I would lean towards the actinolite-tremolite group as well. Unless it is an inaccurate colour rendition, the blue-grey hue reminds me more of the tremolite end of the series.

13th Apr 2018 17:25 UTCDonald B Peck Expert

I, also, think it is an amphibole, not a pyroxene. But to check, can you get a photo of the end of a crystal (termination). If it has cross-sectional angles of about 122^o and 58^o it is an amphibole. Pyroxenes are close to being square in cross-section.

13th Apr 2018 18:33 UTCJoshua Chambers

Thanks for the replies guys!

Thanks Scott for the adularia suggestion. Definitely looks like it.

As to the 'epidote', I may have to get it analysed. I will note actinolite-tremolite as a possibility; thanks Gregg.

I've been looking for terminations, but it's really difficult the see any x-sectional angles when the xls are fibrous. Here are some photos I took of the terminations.

I did find some vitreous, prismatic xls which you could see angles in, but i'm pretty sure these are quartz xls. They are slightly green (prase?).

Cheers

Josh

13th Apr 2018 18:42 UTCFrank Craig

I've analyzed hedenbergite from Tuscany - It's hedenbergite. Of course, that doesn't mean that this one is hedenbergite, but I have seen pyroxenes with this habit. Like the amphiboles, pyroxenes are difficult to label without analysis.

1st May 2018 17:17 UTCLuca Baralis Expert

"The Torre di Rio distal iron skarn, hosted in calc-schists, is located southwards of the Rio Marina deposit, placed on the eastern coast of the island of Elba. The skarn body shows a spectacular mineral zonation, with hedenbergite, ilvaite and epidote domains, accompanied by minor amounts of quartz, carbonates, sulfides, and oxides. "

From: http://www.unil.ch/geoleman/files/live/sites/geoleman/files/shared/Photos/photosMaster/Abstract_Arbiol.pdf

Hedembergite skarn makes the matrix for the well known prase quartz from:

https://www.mindat.org/loc-49849.html Porticciolo di Rio Marina

and from:

https://www.mindat.org/loc-2153.html Torre di Rio - Santa Filomena

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