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



chromium, partly vanadium in Russian specimens of pyromorphite having 

 been stated, it may be supposed that the red pyromorphite from Leadhills 

 owes its characteristic coloration to one of the two elements named before. 



An examination of a great number of cabinet specimens from Leadhills 

 gave no satisfactory result. I could not find any red pyromorphite, as de- 

 scribed by Professor Wohler, on the specimens at my disposal, and must 

 consequently leave unproved the above-stated supposition concerning the 

 colouring-substance of red pyromorphite. A cabinet specimen, dating 

 from the years 1820-1825, gave me, however, the proof that the specimens 

 of cerussite found at Leadhills during this period were not completely 

 free from an admixture of molybdenum and vanadium. I succeeded in 

 rinding out a specimen of crystallized " vanadine-molybdate of lead " from 

 Leadhills so strikingly different in crystallographical and chemical cha- 

 racters from its nearest allies, wulfenite and descloizite, that I am authorized 

 to consider it as the type of a new species, for which I propose the name 

 of " eosite," alluding to its saturated aurora-red colour. 



§ 1. Parayeneiic relations of Eosite. 



The cabinet specimen on which I have found the crystals of eosite has 

 been in possession of the Imperial Museum since 1828 ; it must therefore, 

 as remarked above, date from the years between 1820 and 1 825. Its matrix, 

 abundantly beset with crystals of cerussite, is cellular, ochreous galena. 

 The crystals of cerussite, about 3-8 millimetres in size, bear the aspect of 

 plates, and are greenish yellow ; some of them completely fill up a deep 

 cavity in the ochreous matrix, others are scattered on the surface of the 

 specimen. This cerussite, as also some parts of the matrix, is in several 

 points covered with small moss-like aggregations of delicate and minute 

 acicular yellow crystals. If such a fascicular aggregation is detached, and 

 the concentrically grouped acicular crystals taken away, their nucleus is 

 found to be a very small red crystal fixed on cerussite. When examined 

 with a powerful magnifying-lens, the specimen shows about twenty such 

 minute red crystals more or less scattered over the surface of the cerussite, 

 wrapped up, some of them entirely, others only by half, in the above- 

 described fine yellow acicular crystals. As was subsequently proved by 

 precise determination, the minute red octahedra are eosite, and the yellow 

 acicular crystals are pyromorphite. 



These last crystals, being only |-1 millimetre in length and about 

 millimetre in thickness, could only be determined by the aid of the micro- 

 scope. 



Thev are yellow, pellucid or transparent, very brilliant, with light-yellow 

 streaks. The microscope shows prismatic planes without any distin* 

 guishable terminal planes. As previously for my investigations on labra- 

 dorite, I used for the measurement of the angles of the prismatic planes 

 a vertical circle adapted above the horizontal table of the microscjpe, 

 whose axis bears the object to be measured beneath the microscope's focus ; 



