Calcite

Variety Cobaltian calcite

Origin: Mupine, Shaba, Congo

 

  
Sample size: 4 x 2 x 2 cm
 
  
Sample size: 3x2x1cm
 
  
Sample size: 2 x 2 x 2 cm
 

Photo courtesy of: 

Tom Loomis

Dakota Matrix Minerals

 

 

Terlingua-type calcite. This blue fluorescence is actually phosphorescence. The energy of the 254 nm (short wave) UV is believed to be absorbed by cerium and then photochemically transferred to europium, which fluoresces blue. Since there is a visible delay at the start of the fluorescence (first pink, then blue) and a long lived phosphorescence, we should call this phosphorescence instead of fluorescence.
Under a somewhat shorter wavelenght of UV (350 nm peak) the pinkish fluorescence turns to an almost straw-yellow colour. This is probably caused by the blue fluorescence/phosphorescence that is starting to show. Removing the UV-source reveals a short-lived blue phosphorescence.
This is the typical fluorescence under 366 nm UV. The activator probably is manganese with some co-activator, most likely one or more of the rare earth elements. Photo was taken under a well-filtered blacklight (true blacklight with wood-glass mantle).
Origin: Santa Eulalia Mining district, Mexico
Owner: Axel Emmermann
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  • Photo courtesy of: 

    Axel Emmermann

    Homepage

     

    Calcite twin with stilbite
    Origin: Malad, Bombay, India
    Sample size: 9 x 8 x 7 cm
     
     
    Origin: Jalgaon, Maharashtra, India
    Sample size: 4 x 3 x 2 cm (including the points)
     
      
    Calcite on fluorite
      
      
    fluorite intergrown with calcite on quartz
    Origin: Mahodari, Nasik, India
    Sample size: 8.5 x 5.5 x 4.5 cm (top), 12 x 10 x 5 cm (2nd/bottom row)
     
      
    Calcite on scolecite
    Origin: Jalgaon, Maharashtra, India
    Sample size: 4 x 3 x 2 cm (including the points)
     
      
    Origin: Bamburi, Maharashtra, India
    Sample size: 8 x 6 x 5 cm
     
      
    Calcite on barite
    Origin: Wessels Mine, Kalahari, South Africa
    Sample size: 13 x 9 x 8 cm
     

    Photo courtesy of: 

    Rob Lavinsky

    The Arkenstone

     

     
    Origin: Boral Limited quarry, Bundoora, Victoria, Australia
    Sample size: crystals up to 7 mm long (top), A 60mm wide cavity full of ferroan calcite crystals (bottom)
    Sample owner: Keith & Margaret Brown
     
     

    Photo courtesy of: 

    Steve Sorrell

    Crocoite.com

     

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