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PhotosWillemite - Franklin Mine, Franklin, Franklin Mining District, Sussex Co., New Jersey, USA

23rd Dec 2012 20:23 UTCPeter Chin Expert

Willemite, Calcite

Franklin Mine, Franklin, Sussex County, New Jersey, USA

Uploaded by Modris Baum

Fine grain white mineral is likely calcite in view of its orange fl. Some years ago, I investigated some of the fl. "roeblingites", a few of which after EDS and/ or XRD analysis, were determined to be fine grained calcite (no discernible cleavage). Has it been tested with acid?

23rd Dec 2012 22:37 UTCModris Baum 🌟 Expert

Hi Peter,

Yes. There is no fizzy reaction. (But I did not wait to see if it would eventually dissolve.)

Modris

23rd Dec 2012 22:56 UTCModris Baum 🌟 Expert

OOOOPS! I take that back. It does fizz. I must have imagined that I tested it before.

Case closed. It's just fine grained pinkish, not very brightly fluorescent, calcite.

Thanks Peter. And shame on me ...

Modris

23rd Dec 2012 22:57 UTCSteven Kuitems Expert

Hi Modris and Peter, I think the answer is a mixture, as in manganoan calcite and possibly a serpentine. When looking at the non willemite areas there appears to be some light brown mixed into the pink, weakly fluorescing, carbonate. If there is enough mixing of the two it will definitely slow down any reaction time to the HCL.

Merry Christmas,

Steve.

23rd Dec 2012 23:05 UTCModris Baum 🌟 Expert

Hi Steve,

You are probably right. Maybe I just hit a "slow" spot the last time I tested.

Then again, maybe I just dreamed that I tested it.

Anyway, the spot I tested this time clearly bubbled.

Thanks - Modris

23rd Dec 2012 23:41 UTCModris Baum 🌟 Expert

Peter & Steve,

It turns out that there is actually some large grained calcite with perfectly good cleavage on the specimen.

It is just on one side of the very bottom but a small section can be seen in the far right corner of the photo.

(It is a bit grayer looking than the rest of the matrix.)

This has a very sharp contact with the more fine grained stuff but is separated by from the latter by an apparent reaction band of a few mm (also visible in the photo if you know that it is there.)

Interestingly, the coarse grained calcite is not significantly brighter in UV than the fine grained stuff.

But now that I stare at the UV response longer (thereby no doubt ruining my eyesight), I think I'm seeingn some hardystonite like deep blue mixed in.

Could it be a mixture with the latter? Or am I now hallucinating too?

Modris

24th Dec 2012 00:59 UTCPeter Chin Expert

Well Modris, perhaps, you should give your eyes a rest ! Next you might be seeing Modrisbaumite!

As to a fine grain mixture of hardystonite and calcite, may be. But, if the "mineral" in question is a mixture, I would suggest that it is a fine grain mixture of dolomite and calcite, in which case, you would have a diminished orange fl response. Such mixtures are well documented.

24th Dec 2012 03:41 UTCSteven Kuitems Expert

Modris, these carbonate mixes pop up all over the Franklin/Sterling ore bodies. There are many possible species as Peter and I have suggested. I am not familiar with hardystonite doing this but you never know at Franklin...if it's possible it may be found. You might even be able to match the red fluorescing areas in the UV photo with the less altered calcite in white light. I have seen very fine grained blue fluorescing sphalerite in these mixtures that is colorless in white light but shows up in long wave UV. Try long wave UV responses also and see what happens.

Steve.

24th Dec 2012 03:48 UTCModris Baum 🌟 Expert

Peter and Steve,

Thanks. I will take both of your suggestions :-D

24th Dec 2012 04:10 UTCSteven Kuitems Expert

Just another thought on this mish-mosh. Dunn 1995 mentions zonation and variation in Ca, Mn, Mg in the carbonates so the possibilities of chemical variations adds complexity to the mix and around the boarders of the various carbonate grains themselves. The species mentioned are calcite, kutnahorite, dolomite, and rhodochrosite as well as other non-carbonate species mixed into these. The unidentified light brown material may have a quenching effect on the fluorescent response of the carbonate(s) in the mish-mosh. It would be nice to find someone to do thin section optical analysis on these mixes...perchance someone doing thesis work? Hoping there will be some young student out there with an interest in the Franklin/Sterling district. Another unsolved mystery of the deposit yet to be solved or explained.

Steve.

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