90 On the Composition, of Blende. [Aug. 



distinguished by the name of block jack. It is much more com- 

 mon in veins Than in any other situation ; and as galena ahounds 

 most in transition rocks, the same ride holds with blende. Thus 

 it is found at Lead Hills, which are situated in a transition country, 

 and accompanies the lead ore which is so abundant in the north of 

 England, and which occurs likewise in a transition country. But 

 we must not suppose that galena and blende are confined to tran- 

 sition districts ; for we find lead mines in Great Britain both in 

 primitive and fioetz formations. Thus the lead mine of Strontiau 

 in Argyleshire is a vein traversing a gneiss mountain. At Huel 

 Anne in Cornwall bath galena and blende occur in a vein which 

 traverses clay slate. But it is daily becoming more and more pro- 

 bable, th.it all the granite and clay slate in Cornwall belong to the 

 class of transition rocks. On the other hand, Derbyshire, so pro- 

 duct ve in lead mines, and containing many veins which yield both 

 t' • I i a and blende, seems to belong altogether to the class of floetz 

 ]<> rks. 



< have never myself seen any vein completely filled with blende. 

 h was always accompanied by other minerals; and galena and fluor 

 spar are almost never failing attendants. 



We cannot reeognize either in Theophrastus or Pliny, any de- 

 scription which would lead us to suppose that blende had been dis- 

 tinguished by tbc ancients as a peculiar mineral. The first notice 

 o!' it which J have met with occurs in the treatise of Agiicola, De 

 Naturd Fossiliwm, published, I believe, in 1516*. He gives it the 

 name of galena inctnis, and mentions it in the following terms. 

 Galena vera inanis, sive lapis plumbarius mentis, Licet in nigrore, 

 spl-ndelqne ipsa plumbario laptde, el arena; colore simiiis, omuino 

 (Minis argenti tt plumbo expers. Quorum partem, si in fornace 

 Jiieril simul conjecta, disperdit ac drnipat. De Nulitra Fossilium, 

 lib. x. p. 365. The term galena inanis may be considered as a 

 kind of Latin translation of the German word blende, which was 

 given to ibis mineral by the miners, because it had a considerable 

 resemblance to galena, but no lead can be extracted from it. For 

 the same reason, it was distinguished among mineralogical writers 

 by the name of picudo-^aleiia. 



Mineralogists, after they began to arrange minerals into an arti- 

 ficial system, were long at a loss about the position of blende ; 

 because they were ignorant of its composition. Brandt, a cele- 

 brated Swedish chemist, showed in 1735, that it contained zinc; 

 and soon after, Von Swab pointed out a method of extracting that 

 metal from blende." 1 cannot find any notice of blende in the 

 long dissertation on zinc by Mr. Pott. Indeed he expressly says, 

 that there are no ores of zinc. Of course he must have been igno- 

 rant both of the composition of calamine and blende. But in 1/16', 

 Margraaf informs us that blende contains zinc, and describes an 

 ea^v process by which that metal may be obtained from it.f Mar* 



« Ikrgman, Opu.c ii. £13. + Mar^raaf, Opusc. i. 101. 



