Hyalosiderile. 307 



Ural produced 286 puds, which gave 5700 kilogrammes of 

 metal, having, a value of nineteen millions 500,000 francs. 

 The mines of all Europe together do not produce annually 

 more than 1300 kilogrammes. Those of Chili yield only 

 3000, and all Columbia furnishes only 5000. 



The Ural yields at present as much gold as was ever ob- 

 tained from Brazil at the time when its mines were most pro- 

 ductive. The maximum, which took place in 1755, was 6000 

 kilogrammes of gold. At present Brazil yields only 1000. — 

 Brewster's Journal. 



ON HYALOSIDERITE, BV PROF. BRE1THAUPT. 



Professor Walchner has given a very accurate mineralogical 

 description, and also a chemical analysis of this mineral *. Its 

 locality is that remarkable hill, named Kaiserstuhl, in Baden, 

 which is composed of members of the secondary trap series. 

 At first sight, it might pass for a new mineral ; but Professor 

 Walchner communicated to me his doubts as to its being a 

 new species, and remarked, that it was probably only a variety 

 of olivine. On examining some specimens, I found that it 

 bore the same relation to chrysolite that achmite does to au- 

 gite, viz. having an inferior hardness, and very low lustre in 

 the compact fractured surface. Measurement proved, that 

 the hyalosiderite is a variety of chrysolite, but in a state of 

 partial decomposition. This decomposed condition explains 

 the difference in chemical composition from chrysolite. It is 

 worthy of remark, that when a mineral is altered by weathering, 

 that the open cleavages remained but little affected. This 

 is most striking with the felspar family, as in orthoklase, which, 

 when so much decomposed as to be easily pressed into a kind 

 of porcelain earth between the fingers, yet retains its most 

 obvious cleavages. But it is without lustre in the direction 

 of the compact fracture. M. Kiihn, inspector of the royal 

 porcelain manufacture at Meissen, has, with an ceconomical 

 view, undertaken a chemical examination of the orthoklases, 

 from Aue near Schneeberg. He finds that, in those varieties 

 which are the least decomposed, there is a smaller quantity of 

 potash and more alumina, than in the fresh or unaltered va- 

 rieties % while the more completely decomposed afford no 

 potash, but more alumina. These examples, we think, are suf- 

 ficient to prove, that a mineral can only be considered as a 

 new species, when it possesses essential differences from all 

 known species, and can be examined in a fresh state. It also 

 leads to erroneous views as to composition, if the mineral is 

 examined, not in a fresh, but in a decomposed condition. — 

 Edinburgh New Philosophical Journal. 



* See Phil. Magazine, vol. lxiii. p. 181. 



2 Q 2 HYPOTHESIS 



