Comparison of Three Different Varieties of Green Sodalite and their Tenebrescense

The image to the left was taken with the specimens in their fully “tenebresced” state (5 minutes of exposure to SW UV). The image was taken with a 4 second exposure at F8 under (LW + SW) UV.

Seven images below illustrate the different states of tenebrescense in three different pieces of green sodalite. These pieces were all found in the same location. 

• Image 1 - Natural light
• Image 2 - Long-wave (initial)
• Image 3 - Long-wave (tenebrescent)
• Image 4 - Short-wave (initial)
• Image 5 - Short-wave (tenebrescent)
• Image 6 - Composite flash picture (tenebrescense + UV)
• Image 7 - Tenebrescense (natural light)

Image 1: Three specimens under natural lighting (flash). 

The center large specimen (“Chameleon Sodalite”) has a large amount of aegirine associated with it and exhibits the deepest color change (tenebrescense - typical of those associated with aegirine). It also has a gemmy non-tenebrescent area colored a deep blue/green (also typical).

Lower right - typical highly tenebrescent sodalite.

Lower Left - although very slightly tenebrescent, I call this type “non-tenebrescent”. It is typically much coarser grained than the other two.

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Image 2: 2 second exposure under LW UV - the specimens have not been exposed to SW UV, thus have not “tenebresced”.

FL is pretty much the same except in the gemmy areas of the larger piece. these areas all exhibit this duller rust color - eventually almost losing their ability to FL (see below).

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Image 3: Same 2 second exposure under LW UV, but after the specimens were exposed to SW UV and are in their tenebrescent state.

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Image 4: 6 second exposure to SW UV immediately after turning the light on. It takes time for the tenebrescense to setup, so I call this the initial non-tenebrescent state under SW.

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Image 5: 6 second exposure after 5 minutes of SW UV. Note the deep rust color of the piece at the lower right, and the almost completely quenched FL of the center specimen.

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Image 6: An interesting picture emphasizing the tenebrescense. This is a 6 second time exposure with a flash at the beginning of the exposure. Thus the natural light image has been superimposed over the time exposure of SW FL.

The amount of orange (brighter FL) indicates less tenebrescense.

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Image 7: Flash picture of pieces immediately after long term exposure to UV (10 minutes+) - with no visible light on the specimens prior to picture.

Note the deep purple of the center piece, the pleasing purple of the lower right specimen, and the virtual lack of tenebrescense of the lower left specimen.

Rarity appears as follows:

• Deeply tenebrescent - rarest
• Non-tenebrescent - next rare
• Tenebrescent - most common (of this batch)

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Frozen tenebrescense (cold and wet)