22 



cinth red bead : to acid of sugar, it readily yields its menac 

 contents, which furnishes the chai'acteristic precipitate of 

 this genus. Klaproth and Lampadius have given us the 

 constituent ingredients, 8 or 9 per cent, menac calx, and 2 

 or 1 calx of iron. It is probable, however, that the propor- 

 tion of menac calx is over-rated ; it appearing evident, from 

 the description accompanying the analysis, that there had 

 been no care taken to select tlie nigrine from the grains of 

 mtile which accompany it. 



GEOGNOSTIC OCCURRENCE. 



The nigrine has been liitherto found only at Ohlapian, in 

 Transylvania, in alluvial hills, consisting of yellow sand, in- 

 termixed Avith fragments and bowlders of granite, gneiss, 

 and mica slate, and from which gold is obtained by washing. 

 This gold is the purest found in Transylvania ; a circum- 

 stance sufficiently indicating, that it belongs to a different, 

 and, consequently, eajlier formation, than the usual Tran- 

 sylvanian native gold, which occurs there in clay porphyry, 

 grey Avacce, and gi'cy Avacce slate, and belongs to the brass 

 yelloAv variety, from the considerable alloy of silver Avhich it 

 contains. In these strq^im Avorks, the nigi'iue is obtained at 

 the same time Avith the gold, and comes to us intermixed 

 Avith grains of 'rutile, oriental garnet, native iron, cyanite, 

 and common sand; Avhioli renders it extremely probable, that 

 this fossil, also, is a native of the primitive mountains. 



FOURTH 



