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XLVIII. On Phosphorite from Spain. 

 By David Forbes, F.R.S., fyc* 



THIS mineral was some time back forwarded from Spain for 

 the purpose of being submitted to chemical examination ; 

 it was stated to occur in the district of Estramadura in South- 

 ern Spain in large quantity. 



The specimens received, though in large blocks, consisted of 

 the pure phosphorite, apparently uncontaminated and unaccom- 

 panied by any other minerals; the mineral itself was massive, 

 and, on breaking, the fracture was uneven and earthy, disclosing 

 at the same time a slightly radiating dendritic structure, but no 

 trace whatever of crystallization. The colour of fresh fracture 

 was chalk-white, but weathered surfaces frequently showed a 

 dirty or rusty white colour externally. Lustre earthy ; opake ; 

 streak and powder dead white. 



Hardness about 4*5 on the scale, or immediately below apa- 

 tite, by which it was scratched. The specific gravity was taken 

 on two distinct specimens, and found to be 3*00 and 2'92 re- 

 spectively at 60° F. 



When the powdered mineral was heated over a lamp in the 

 dark or thrown on to a nearly red-hot plate of iron, it quickly 

 glowed, emitting an extremely beautiful and slightly greenish- 

 yellow light, which passed off before the mineral attained a 

 visibly red heat. As Mr. Phipson, in his treatise on Phospho- 

 rescence, states that minerals which, after having been heated, no 

 longer emit the characteristic phosphorescent light upon reheat- 

 ing, again recover their fluorescent property upon being exposed 

 to the sunlight, the experiment was tried several times and with 

 various modifications, but failed even after many days' exposure 

 to the sun's rays : this was also the case when the mineral, after 

 heating once, was cooled in the dark and again reheated. In order 

 also to see if the loss of moisture in the first heating had any 

 relation to the phosphorescent property, another portion, after 

 heating, was thrown into water and kept in the sun under water 

 for many days ; on being air-dried and reheated no signs of phos- 

 phorescence could be detectedf. 



In order to examine whether, as is the case with the mineral 

 Gadolinite J, the phenomenon of fluorescence, on heating, might 



* Communicated by the Author. 



t Mr. Phipson states that the fluor-apatites only are phosphorescent, 

 and that this is not the case with the chlor-apatites. On examination, 

 however, the fine crystallized true chlor-apatites from Krageroe in Norway 

 emitted, on heating in the dark, a most distinct slightly greenish-yellow 

 light, though not quite so bright as the above phosphorite. 



X Gadolinite, when heated, glows suddenly and increases in density, 

 being, after ignition, about 5 per cent, specifically heavier than before. 



