308 W. P. Headden — Some Phosphorescent Calcites. 



other members of the £roup which occur in the mineral are 

 present in the purple portion also and probably play but a 

 small part, if any, in imparting this property of phosphor- 

 escing to the calcite. 



The phosphorescence is confined to the yellow portions of 

 the mineral, and those having the deepest yellow color, such 

 as pass into a brownish yellow shade, show the strongest phos- 

 phorescence. Our failure to detect any organic coloring matter 

 suggests very strongly that we are to find the cause of the 

 phosphorescence in the presence of some element whose salts 

 are yellow. My interpretation of the facts is that they point 

 to the yttrium group or some member of it, whether it is at 

 present known to chemistry or not, as the cause of this property. 

 It may be only a coincidence, but it is a fact that the deeper 

 brownish yellow portions of the calcite are strongly suggestive 

 of the brownish yellow of xenotime, and had phosphoric acid 

 been present in this calcite in more than a very minute trace, we 

 might, with a fair show of reason, have inferred the presence 

 of the phosphate of yttria, but there is only a trace of phos- 

 phoric acid and the phosphate of yttria cannot be present. I 

 do not, however, intend to convey the impression that yttria 

 may not be the cause for which I have been searching, for at 

 the present time I am inclined to think that it is. 



It may seem marvelous, even to the chemist, that an amount 

 of any substance so small as we are evidently dealing with in 

 this case, should be capable of producing such striking and 

 beautiful effects as I have endeavored to describe. It is 

 marvelous but not incredible. Sir William Crookes has been 

 able, by means of the phosphorescent spectrum, to detect one 

 part of yttria or samaria when diluted with one million parts 

 of lime, and the one part of samaria continued to cast its 

 shadow, so to speak,- on the spectrum in the presence of two 

 millions -five hundred thousand parts of lime. 



The figures deducible from my analyses are scarcely sugges- 

 tive of such infinitesimal quantities as these, still it is possible 

 that the substance actually causing this wonderful sensitiveness 

 to sunlight and imparting the power to give it out again for 

 so long a time may be present in no greater quantity than one 

 part in two millions fi^e hundred thousand. 



The limit of my present progress is the establishment of a 

 probability that these calcites owe their property of becoming 

 phosphorescent on insolation to the presence of some member 

 of the yttrium group which is represented by 13 parts in each 

 100,000 parts of the calcite. 



Colorado Agricultural College, Fort Collins, Colo. 



