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PhotosCurious why this photo was assigned to user gallery only

19th Oct 2020 21:53 UTCBryan Davis

Poor photo? Misidentification? Incomplete labelling?

Also, more generally, is it acceptable to do vertical comparisons like this for daylight/UV? Should I also upload the individual photos? Is vertical preferred over horizontal comparisons? Just trying to improve my photos, and appreciate any input/feedback.

Thanks!

19th Oct 2020 22:46 UTCJolyon Ralph Founder

I think the labelling is insufficient. And what are you trying to show here? Quartz is listed as the primary mineral but I can't see the quartz being important here unless I'm missing something.

20th Oct 2020 01:20 UTCBryan Davis

Great point, I was focusing on the picture and not the description. I've never personally seen quartz crystals on the same specimen as franklinite and fluorescent willemite. After searching through the photos on mindat I did not see any other pieces with this combination, so wanted to provide an example. I will rewrite the description to emphasize why I think its a worthwhile photo.

20th Oct 2020 02:30 UTCKeith Compton 🌟 Manager

And I guess - that you are sure it is on quartz and not calcite (which seems to be more the norm) ?

20th Oct 2020 07:49 UTCAlfredo Petrov Manager

Wouldn't it be red in the fluorescent photo if it were calcite? Or does Franklin also yield non-fluorescent calcite? (Just asking - I'm no Franklin expert by any means.)

20th Oct 2020 11:37 UTCKeith Compton 🌟 Manager

I'm no Franklin expert either Alfredo (but I should have considered the fluorescent issue).

Yes most is fluorescent, however:

In Pete Dunn's book "Franklin and Sterling Hill, New Jersey: the world's most magnificent mineral deposits, Vol II at p.61, states that:

"Calcite from the Franklin Marble fluoresces but rarely."

So apparently non-fluorescent calcite is found there.

20th Oct 2020 15:57 UTCTony Nikischer 🌟 Manager

There is much calcite from Franklin and Sterling that is not fluorescent.

20th Oct 2020 21:38 UTCBryan Davis

I didn't call out the composition of the "matrix", but my assumption was non-fluorescent calcite. I thought that being so close to quartz may have sapped the fluorescent activators or something, but I am also not a Franklin expert.

20th Oct 2020 09:59 UTCHerwig Pelckmans

And Bryan, when I look at the description, I don't see anything mentioned about the white/cream colored mineral that makes up the specimen (what I would call "the matrix" in this case). According to your description, it is not quartz. So what is it, some kind of feldspar?

I feel this should be mentioned in the description as well.

Cheers, Herwig

(Belgium)

20th Oct 2020 21:35 UTCBryan Davis

My assumption was non-fluorescent calcite, but I have not tested it so did not want to make a guess. I identified the quartz crystals based on the shape of the faces under a loop.

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