and its Unique Properties. 27 



strongly phosphorescent under these rays. An exposure of 

 half a minute caused three cut gems to glow first a golden-pink, 

 and then white for ten minutes. The glow was visible through 

 two thicknesses of white paper, which was held over it. A 

 large crystal excited for five minutes afterward affected a sen- 

 sitive photographic plate. * Another crystal, exposed for ten 

 minutes, was laid for five minutes on a sensitive plate. f The 

 resulting auto-photograph was clear and distinct, but presented 

 a very curious aspect not seen by the eye — as of a misty or 

 feathery outflow from the side and termination of the crystal, 

 suggesting an actual picture of the invisible lines of force. The 

 other varieties of spodumene, mineral material and cut gems, 

 failed to show this property. We are not yet in a position to 

 offer a satisfactory explanation of the above. 



Whereas kunzite is so responsive and fluorescent and so 

 beautiful upon exposure to the X-rays, it is, however, like all 

 silicates, opaque to the ray itself. Four crystals weighing 100, 

 200 and 400 grams each, were exposed to the Roentgen ray for 

 two minutes. They became first a beautiful rose-orange, then 

 assumed a white phosphorescence, and at the end of forty-five 

 minutes there was still a faint residual glow. Two minutes 

 exposure to the X-ray caused them to print a perfect auto-type 

 (herewith shown, Hg. 2). The glow in all instances showed first 

 a rose-orange color, then a pale pink, finally resolving into a 

 white fluorescence ; the auto-print shows the feathery outlines 

 of light or energy thrown out by the crystal. 



5. Conduct with radium preparations. — Exposed for a few 

 minutes to radium bromide with a radio-active strength of 

 300,000 (uranium being taken as unity), the mineral becomes 

 wonderfully phosphorescent, the glow continuing persistently 

 after the removal of the source of excitation. The bromide was 

 confined in glass. Six hundred grams of kunzite crystals were 

 thus excited with 127 milligrams of the radium bromide in five 

 minutes. The effect is not produced instantaneously but is 

 cumulative, and after a few moments exposure the mineral 

 begins to glow, and its phosphorescence is pronounced after the 

 removal of the radio-active body. The luminosity continued 

 in the dark for some little time after the radium was taken 

 away. Xo other varieties of spodumene examined, including 

 hiddenite, gave like results. In this respect, as with the 

 Roentgen rays, the kunzite variety stands by itself. 



When pulverized kunzite is mixed with radium-barium 

 chloride of 240 activity or carbonate of lower activity, the 

 mixed powder becomes luminous and apparently remains so 

 permanently ; i. e., in several months no loss has been observed. 



* Science, X. S., xviii, 303, 1903. 



f This was made by Dr. H. G. Piffard of New York City. 



