Time-Exposure Sequence
(All FL images taken at F2.8, 1 second exposure)

This time-exposure sequence illustrates the darkening of a highly tenebrescent piece of green sodalite (“Chameleon Sodalite”) under natural lighting and fullwave UV (LW + SW).  It automatically cycles through a set of 16 images showing the color change under both natural lighting and FW UV.

• 13 images were taken at ten second intervals, starting with a “non-tenebresced” piece.
• Three images were taken at one-minute intervals at the end of the cycle.
• After 5 minutes no appreciable darkening was observed
• The color changes are most significant in the first 30 seconds, and then very gradual for the next 5 minutes. 

Static Images

Tenebrescent

Non-Tenebrescent

Image 1 Natural Light - Shows the specimen after 10 minutes of exposure to SW versus the specimen after 1 minute of exposure to 4500k halogen lights

Image 2 Fullwave UV - FL photo of specimen under FW UV after 10 minutes of exposure to SW versus the specimen as it fluoresces immediately after UV light is applied to a “non-tenebresced” state.

Image 3 - Shortwave only. FL photo showing the difference in fluorescense - only under SW - between the tenebrescent and non-tenebrescent states. Due to the quenching caused by the tenebrescense these images were exposed for 16 seconds (see image below for a 6 second exposure).

 The shortwave image to the right was taken at F8, 6 seconds when the piece was in a full tenebrescent state - note the very dim FL. In order to show the color change the F-stop had to be opened completely and the time-exposure set to 16 seconds (see Image 3 above).

It appears that the tenebrescense significantly quenches the FL response under SW. Under LW the response is a deep rust as the Image 2 above shows.

But.... this is a magnificent display specimen. Brilliant yellow/orange under LW, but once the SW lamp takes over the deep rust glow is unlike any other fluorescent.