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Calcite is acting strange under UV
  
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Forrestblyth




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PostPosted: Aug 08, 2022 07:43    Post subject: Calcite is acting strange under UV  

My recently acquired calcite specimen behaviour under UV is confusing me.

It glows a very strong bright yellow. It also continues to glow for 3 seconds after UV exposure. Most of my other calcites glow red. there appears to be an additional secondary white crystal present and I am wondering if this is the cause of this strong reaction. But I don't see the normal red colouration I would have expected from the main bulk of the specimen that I am used to from calcite. I am confused why this is so.
The very strong yellow reaction does not seem to record on my camera well yet it is extremely prominent to the eye.

I have tried to capture a few shots of the secondary crystallization but it's very small and is a challenge for my photography skills

The specimen measures about 100mm x 50 x 20

The main diamond shaped calcite crystals measure about 5 to 7 mm and the unknown white secondary crystals are about 0.5 mm.



20220808_125951.jpg
 Mineral: Calcite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: Calcite crystals size around 5 mm
 Description:
 Viewed:  1218 Time(s)

20220808_125951.jpg



20220808_130146.jpg
 Mineral: Calcite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: Specimen size: 100 x 50 x 20 mm
 Description:
 Viewed:  1217 Time(s)

20220808_130146.jpg



20220808_124245.jpg
 Mineral: Calcite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: Calcite crystals size around 5 mm
 Description:
 Viewed:  1212 Time(s)

20220808_124245.jpg



20220808_124225.jpg
 Mineral: Calcite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: Calcite crystals size around 5 mm
 Description:
 Viewed:  1215 Time(s)

20220808_124225.jpg



20220808_124310.jpg
 Mineral: Calcite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: Calcite crystals size around 5 mm
 Description:
 Viewed:  1215 Time(s)

20220808_124310.jpg


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Peter Megaw
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PostPosted: Aug 08, 2022 08:09    Post subject: Re: calcite is acting strange under UV  

Calcite has a very wide range of fluorescent responses stemming from a wide range of trace amounts of activators and sensitizers. This is a VERY deep rabbit hole you have headed down...

The orange-red-pink you are used to seeing is caused by manganese (orange activator) and lead (red sensitizer). That you are accustomed to this suggests many of your calcites are from high temperature hydrothermal base and precious metal deposits (veins, replacements, porphyries).

But calcite occurs in an almost infinite variety of geological environments where different activators may be present. Mercury for example causes a strong blue-white fluorescence with extremely persistent fluorescence when the UV source is removed (also called phosphorescence). There are some localities, like Terlingua, Texas where the calcite fluorescence lingers for up to 30 seconds.

Organic materials can also provoke fluorescence, most commonly in oranges to creamy yellows or off-whites. These also can show persistent fluorescence, but generally it only lasts a few seconds.

Your piece comes from Nanisivik...this is a Mississippi Valley Type deposit, formed from low temperature "oil field" brines. This means the fluids carried plenty of organics, which are probably what is causing your fluorescence.

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Peter Megaw
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PostPosted: Aug 08, 2022 08:11    Post subject: Re: Calcite is acting strange under UV  

Sorry, misread locality...not Nanisivik so forget MVT

These Indian deposits are hosted in basalts...so different source and explanation, but still one of hundreds of calcite environments and fluorescence sources

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Jordi Fabre
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PostPosted: Aug 08, 2022 08:35    Post subject: Re: Calcite is acting strange under UV  

I fixed (again) everything for you.

'Remember that if you are publishing a photo of a mineral specimen please fill in all 3 of the above fields'
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Forrestblyth




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PostPosted: Aug 08, 2022 09:26    Post subject: Re: calcite is acting strange under UV  

Peter Megaw wrote:


The orange-red-pink you are used to seeing is caused by manganese (orange activator) and lead (red sensitizer). That you are accustomed to this suggests many of your calcites are from high temperature hydrothermal base and precious metal deposits (veins, replacements, porphyries.


Hi Peter thank you for your knowledgeable answer. You are correct. My normal collecting localities for most of my self-collected calcite specimens are from the heavy metal orefields of Weardale and Caldbeck Fells of the UK. I am not used to material from varied worldwide locations. This is the first time I have actually purchased international material. I visited a mineral show and as well as shelling out on rare English minerals, I was drawn to the unbelievably great value for money Asian specimens that I have never seen before. I am pleased to have found this great learning forum resource that is broadening my knowledge that was limited to local collecting experience.

I have just again looked at this specimen under UV. I am now starting to think that it is surrounding material that is almost back lighting those lovely clear calcite crystals. I checked the reverse side of the matrix that had few larger calcite crystals present. The fine encrusting unknown white mineral was glowing extremely strongly. I must try to see it under microscope to hopefully identify it. It is most interesting and arguably an even brighter luminescence that even my Weardale fluorite.
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Bob Carnein




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PostPosted: Aug 08, 2022 09:37    Post subject: Re: Calcite is acting strange under UV  

Nashik produces many minerals that are candidates for the tiny white crystals. It's unlikely that they have anything to do with the yellow fluorescence of the calcite. Unfortunately, the photos don't show the white crystals clearly enough for a useful guess. They appear to be somewhat bladed, which eliminates some things.

As Peter noted, the fluorescent response of calcite is complex and pretty varied. A "bright" yellow response would be rare, from my experience. But creamy yellow is quite common, as is persistent luminescence.
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Joseph DOliveira




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PostPosted: Aug 08, 2022 09:47    Post subject: Re: Calcite is acting strange under UV  

Forrestblyth wrote:
My recently acquired calcite specimen behaviour under UV is confusing me.

It glowing a very strong bright yellow. It also continues to glow for 3 seconds after UV exposure. Most of my other calcites glow red. there appears to be an additional secondary white crystal present and i am wondering if this is the cause of this strong reaction. But I don't see the normal red colouration I would have expected from the main bulk of the specimen that i am used to from calcite. I am confused why this is so
The very strong yellow reaction does not seem to record on my camera well yet it is extremely prominent to the eye.

I have tried to capture a few shots of the secondary crystallisation but its very small and is a challenge for my photography skills

The specimen measures about 100mm x 50 x 20

The main diamond shaped calcite crystals measure about 5 to 7 mm

the secondary white unknow crystals are about .5 mm



P1019274.JPG
 Mineral: Calcite on Mordenite
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: 4.2x4x3 cm's
 Description:
Calcite crystals to 1.2 cm's that fluoresce yellow under LW 365nm light. While these fluoresce bright yellow, they do not maintain the fluorescence when the UV light is removed.
 Viewed:  1103 Time(s)

P1019274.JPG



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Forrestblyth




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PostPosted: Aug 08, 2022 13:52    Post subject: Re: Calcite is acting strange under UV  

Bob Carnein wrote:
Nashik produces many minerals that are candidates for the tiny white crystals. It's unlikely that they have anything to do with the yellow fluorescence of the calcite. Unfortunately, the photos don't show the white crystals clearly enough for a useful guess. They appear to be somewhat bladed, which eliminates some .


Hopefully a slightly better close up of secondary minerals. I can now see the bladed form you mentioned. I am now wondering if there are two separate secondary minerals. One bladed and one encrusting form.



20220808_162845.jpg
 Mineral: calcite plus unknown secondary minerals
 Locality:
Nashik District (Nasik), Maharashtra, India
 Dimensions: .1mm to .5mm crystals FOV 20mm
 Description:
Close up of secondary minerals
 Viewed:  1000 Time(s)

20220808_162845.jpg



20220808_163106.jpg
 Mineral: calcite plus unknown secondary minerals
 Dimensions: .1mm to .5mm crystals FOV 20mm
 Description:
Close up of secondary minerals
.1mm to .5mm crystals FOV 20mm
 Viewed:  999 Time(s)

20220808_163106.jpg



20220808_163659.jpg
 Mineral: calcite plus unknown secondary minerals
 Dimensions: .1mm to .5mm crystals FOV 20mm
 Description:
FOV is 20mm
Close up of secondary minerals
 Viewed:  1004 Time(s)

20220808_163659.jpg


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Forrestblyth




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PostPosted: Aug 08, 2022 14:01    Post subject: Re: Calcite is acting strange under UV  

P1019274.JPG
Mineral: Calcite on Mordenite

Thank you for the Mordenite photograph. Interestingly, the large specimen box selection this item came from had examples of Mordenite in the box. I did buy one I and I will look to see if it has uv similarities to the secondary material on my specimen
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Bob Carnein




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PostPosted: Aug 08, 2022 17:56    Post subject: Re: Calcite is acting strange under UV  

Some of the white minerals seem to radiate from a central banded material. That may be quartz crystals on an agate core. I would try the hardness (should scratch a knife blade).
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PostPosted: Aug 08, 2022 18:53    Post subject: Re: Calcite is acting strange under UV  

To me the white crystals look like bladed stilbite, which would be a common associated mineral from that area. Very difficult to accurately identify from the photograph.

Forrestblyth wrote:
P1019274.JPG
Mineral: Calcite on Mordenite

Thankyou for the Mordenite photograph. Interestingly the large specimen box selection this item came from had examples of Mordenite in this box. I did buy one I and I will look to see if it has uv similarities to the secondary material on my specimen

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alfredo
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PostPosted: Aug 08, 2022 22:33    Post subject: Re: Calcite is acting strange under UV  

I agree with Joseph that the little tabular white crystals are stilbite.
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