Radium and Luminosity

Kunzite, almost 7 in hardness, is transparent and pleochroic. Viewed transversely some representative crystals were faintly pink; longitudinally they presented a rich pale lavender colour, approaching amethystine. A characteristic of kunzite crystals is a peculiar etching, apparently effected with solvents. A number of scientific tests have revealed in kunzite a remarkable phosphorescence, not possessed by other varieties of spodumene similarly tested, and its illuminant powers, excited by its bombardment with Rontgen rays, and also by the proximity of a few milligrammes of radium bromide, mark this mineral as unique and of unusual interest to scientists, in addition to its value as a recruit to the first rank of semiprecious stones.

In a description of experiments made upon kunzite Sir William Crookes writes:

But the most interesting thing to me is the effect of radium on it. A few milligrammes of radium bromide brought near the piece of kunzite makes it glow with a fine yellowish light, which does not cease immediately on removal of the radium, but persists for several seconds.

I have found some diamonds phosphoresce brightly under the influence of radium, and have been searching for a mineral which is equally sensitive. I think this lilac variety of spodumene runs the diamond very close, if it does not surpass it sometimes.

The luminosity of kunzite, in response to the artificial conditions already known to arouse it, is thus summed up, in a sentence, by Dr. Kunz:

In a word, kunzite responds to radium, actinium, Rontgen and ultra-violet rays; it is thermoluminescent and pyro-electric. Becomes radescent when mixed in powdered form with radium; becomes incandescent when this mixture is slightly heated, and crystals or gems become beautifully phosphorescent for quite a time by passing a faradic current through it, or if held between the poles of a Holtz machine.

The sole drawback at present to the increasing appreciation of kunzite is that the supply, according to reports in the jewelry trade in New York City, is unequal to the increasing demand. In 1907, according to reports of the United States Geological Survey, about 126 pounds of gem spodumene, selected material, was obtained from the California gem region, but not all of this was the variety kunzite. Albert Dabren, a mining engineer, of Madagascar, has reported that gem kunzite has been found there.