RECORDS. 203 



dumene). Hiddenite, the green spodumene, seems to be non- 

 fluorescent. Impaired by fluorescence are triphane, a yellow- 

 ish-green spodumene, which exhibits pink fluorescence in blue 

 light ; emerald, which shows crimson fluorescence in the upper 

 part of the spectrum, and diamond, with greenish-blue to blue 

 fluorescence excited by several kinds of energy but more or less 

 masked in ordinary light. 



In fluorescent substances excitation produces a certain opa- 

 lescence or milkiness which is sometimes of sufficient strength 

 to be of importance. It cannot be taken as an indication of 

 impurities in the materials. In the white diamond such a phe- 

 nomenon is a detrimental quality. 



Fluorescence affords a simple and positive method of distin- 

 guishing some of the fluorescent gems from imitations. All 

 glass imitations are fluorescent with the color characteristic of 

 glass from which the fluorescent color of the genuine stone differs 

 distinctly. In doublets the cement appears as an opaque film 

 and the components differ in behavior. Artificial pearls of high 

 grade have not been examined, but probably they will behave 

 like the genuine. Artificial or "regenerated" ruby has been 

 examined in a single specimen. It acts like the natural stone 

 in blue light, while with the air-gap spark between iron or 

 aluminum electrodes it has a brighter color than any of the 

 several natural rubies which were examined. The wave-length 

 which excites fluorescence of each substance must eventually be 

 stated. 



The following gems were stated to be non-fluorescent : gar- 

 net, amethyst, Spanish topaz, yellow Brazilian topaz, sapphire, 

 ordinary beryl, possibly Siamese ruby. 



In the discussion of Mr. Levison's paper Professor Kemp 

 expressed the hope that there would be a practical outcome 

 from such investigations which would enable those not experts 

 to detect false or artificial gems ; while Mr. Kunz said that there 

 were simpler ways than the use of fluorescence for the deter- 

 mination of gems, and Professor D. S. Martin emphasized the 

 desirability of getting definite information as to the wave-lengths 

 to which gems respond. 



