272 A. F. Rogers — Collophane. 



It is reasonably certain that all of the above listed min- 

 erals are one and the same. Some of the names have 

 priority over cellophane (Kollophan), hut one of the limi- 

 tations of the law of priority set forth by Dana 9 is that a 

 name may properly be set aside when it "has been lost 

 sight of and has fonnd no one to assert its claim for a 

 period of more than fifty years. . . ." Collophane, or 

 rather its equivalent, collophanite, on the other hand, has 

 been given prominence by Lacroix in his excellent trea- 

 tise 10 on the minerals of France. 



Pyroclasite and pyrogaunite are simply varieties of 

 hard guano. As they contain about 80 per cent of trical- 

 cium phosphate, they are doubtless collophane. In a 

 later paper Shepard says that glaubapatite is the same as 

 pyroclasite. 



Monite is an earthy variety of collophane. Shepard 's 

 analysis does not show any carbon dioxide but specimens 

 free from admixed calcite examined by the writer show 

 decided effervescence in nitric acid. The sulphur trioxide, 

 which was deducted by Shepard, is probably an integral 

 part of the mineral, for specimens free from admixed 

 gypsum give a good microchemical gypsum test. The 

 collophane from other localities sometimes contains the 

 sulphate radical and so does apatite also for that matter. 



Sombrerite is from the type locality for collophane, but 

 it is a phosphatic replacement of coral, while the original 

 collophane is an opal-like substance not due to direct 

 replacement. A specimen of sombrerite in which coral 

 structure is evident has been examined by the writer. It 

 agrees in all essential respects with collophane. For 

 example, it is soluble with effervescence in nitric acid, 

 but is entirely free from calcite. 



Quercyite is undoubtedly a variety of collophane and 

 not a mixture of collophane with a crystalline substance. 

 A specimen in my possession agrees exactly with 

 Lacroix's 11 description and figures, but the apparently 

 crystalline layers, though doubly refracting, are really 

 amorphous. The analyses of quercyite together with 

 the microscopic examination prove its identity with 

 collophane. 



9 System of Mineralogy, 6th edition, p. xliii, 1892. 



10 Mineralogie de la France et de ses Colonies, vol. 4, pp. 561-586, 1910. 



11 Mineralogie de la France, pp. 579-581, figs. 1-2, 1910. 



