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UV MineralsFluorescent Aragonite

1st Sep 2016 22:06 UTCDennis McCoy

I just received this aragonite specimen without any details. It reminds me of some of the Italian aragonites I've seen advertised. Most of the crystals are water clear, with optic qualities like "spar" calcite. Almost all are heavily included with other minerals. (I am also putting a query on the identification forum.)

The photo is taken with a time exposure, under my UV light and "bathed" with my 405nm laser throughout the exposure.

2nd Nov 2016 12:01 UTCHarold Moritz 🌟 Expert

The pink/magenta color is very indicative of calcite. Aragonite fluorescence is usually creamy white, pale yellow or pale blue. Your description of it also sounds like calcite.

2nd Nov 2016 13:15 UTCAlfredo Petrov Manager

Also, aragonite is usually phosphorescent, calcite less commonly.

(Or rather I should say the phosphorescence in aragonite is generally longer-lasting than calcite's.)

2nd Nov 2016 14:37 UTCMichael Hatskel

Another possible test: after being heated (blowpipe, torch), aragonite may crumble and loose its fluorescence, while calcite will remain fluorescent.

Question to the forum: How reliable is that distinction? Do you know of any localities where it doesn't work that way?

2nd Nov 2016 16:45 UTCReiner Mielke Expert

How about showing us a picture in sunlight?

2nd Nov 2016 22:14 UTCJosé Zendrera 🌟 Manager

Typical fluorescence color under long wave of Italian aragonite is red. But if the UV source is not properly filtered then fluorescence appears magenta due to blue visible light mixed with the real fluorescence. That happens when using a UV LED flashlight whose peak is about 400 nm but emiting a lot of blue light too. This can be corrected by fitting a filter.

The conclusion is that identifications based in fluorescence color can be confusing if we are not familiar with the UV source used for photos.

9th Nov 2016 21:30 UTCDennis McCoy

Here are photos of both sides of the specimen in natural light.

9th Nov 2016 21:53 UTCHarold Moritz 🌟 Expert

Look like hexagonal calcite prisms, and not pseudohexagonal cyclic aragonite twins.

9th Nov 2016 22:33 UTCBob Harman

I agree, calcite is favored and under your UV light I see mostly violet reflections from the light rather than creamy yellowish white fluorescence which my Indiana aragonites all display. CHEERS.....BOB

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