458 Dr. A. Schrauf on Molybdates and Vanadates of Lead. [May 4, 



which, being heated to evaporation, leaves on the glass plate a precipitate 

 of fine green colour. 



These alterations are common to both varieties, as also those produced 

 by fusion with bisulphate of potash. The saline substance thus obtained 

 is yellow during fusion; it becomes • reddish during cooling, and deep 

 reddish orange after complete refrigeration. This last coloration may ex- 

 ceed two or three times in intensity the coloration obtained by treating 

 eosite with bisulphate of potash. 



These experiments, merely tried with some few minute fragments, 

 although any thing but decisive, are sufficient for ascertaining the difference 

 between eosite and the vanadates of lead. 



As the dark variety (A) resembles Peruvian eosite, the light variety (B) 

 "bears some resemblance to the dechenite from Schlettenbach. 



This dechenite is likewise of carnation colour, somewhat fainter on the 

 surface than on the recent fracture. The cabinet specimen before me 

 shows isolated crusts, transversely concreted, with globular external sur- 

 face, offering a blackberry -like aspect. A fracture shows these crusts to 

 be concentric agglomerations of minute crystals (1 millim. in size), exter- 

 nally exhibiting only one or two of their planes. Isolated margins may 

 be found by careful inquiry, but I could not succeed in obtaining any 

 measurable angle. The crystalline crust includes a number of spheroidal 

 cavities (similar to those of pisolite), around which the aggregations of 

 crystallized dechenite are concentrically disposed. Greenish pyromorphite 

 appears on the inferior surface of the specimen in question. 



Like the variety B of vanadinite, this specimen is very easily af- 

 fected by moisture. Even when a sheet of paper is held before the 

 mouth, the moisture of the breath is sufficient to produce globular 

 yellowish-grey efflorescences. The streak is orange, verging into reddish 

 brown. 



The action of hydrochloric acid and bisulphate of potash is nearly the 

 same with that exercised on vanadinite, as already detailed. 



A splinter moistened with hydrochloric acid shows a yellow margin and 

 a darker nucleus, in which the vanadium is concentrated. The colour 

 of this nucleus, instead of being very intensely brownish red, is of a rather 

 darker brown than the unaltered mineral. The action of the acid, mani- 

 fested by the progressive darkening and lessening of the nucleus, is, how- 

 ever, less prompt and less evident than when vanadinite is acted upon, and 

 resembles rather the alterations undergone by eosite. The difference lies, 

 however, in the yellowish coloration of the solution around the crystal 

 lying on the glass plate. Alcohol gives rise to the secretion of a gelatinous 

 yellowish-green liquid, which, evaporated by heat, assumes a fine green or 

 bluish-green tint, nearly identical to the tint assumed by vanadinite under 

 the same circumstances. 



Dechenite, melted with bisulphate of potash, gives a deep brownish- 

 yellow substance, reddening by cooling, and finally becoming of a deep 



