SS Mineralogical Notices. 



CHLORITE. BY M. RAMMELSBERG. 



[PoggendorfF's Annalen, vol. Ixxvii. p. 414.] 



According to Rammelsberg, two minerals, Leuchtenbergite 

 and Pennine, certainly belong to chlorite, and should not be 

 separated from it by distinct names. A review of the various 

 analyses which Rammelsberg has corrected and rendered 

 more complete, has led him to the following conclusions re- 

 specting the Chlorites : — Certain varieties of Chlorites occur, 

 which are characterized by containing about 30 per cent, of 

 acid, and by a lesser amount of iron,, such for instance are the 

 Chlorites of Achmatowsk, from Schwarzenstein in Zillerthal, 

 from Mauleon in the Pyrenees, from the river Balschoi Ire- 

 mel, and from the Schischminskian Mountains near Slatoust; 

 further, from Zermatt in the Matterthal Canton Vaux ; and 

 these two latter have been incorrectly distinguished as Leuch- 

 tenbergite and Pennine*. The relation of the oxygen to the 

 magnesia or (FeO) of the alumina, or (Fe^ O^) of the silica 

 and of the water, is for all more or less nearly as 5 : 3 : 6 : 4, 

 and the formula thence deducible is 



(3RO + Si03 + R2 03Si03 + 2HO) + 2MgO,HO. 

 It is however highly probable with respect to the other va- 

 rieties, on account of the difficulty in determining the relative 

 quantities of protoxide and peroxide of iron, that the above 

 relation = 3 : 2 : 4 : 3. To the variety corresponding to this 

 atomic proportion, Rammelsberg gives the name of Chlorite. 

 Its formula is consequently 



3(3RO + Si03) + (2R2 03 + Si03) + 9HO. 



Ripidolite, 3(3RO + Si03) + (SR^ O^ + SiO^) + 9HO, is the 

 name which Rammelsberg assigns to the series of modifica- 

 tions which occur at St. Gothard, in the valley Rauris of the 

 Pinzgau, at the Greiner in the Zillerthal, at St. Christoph, 

 and at Mont des Sept Lacs in Savoy ; they are characterized 

 by a less amount of acid (26 — 27 per cent.), a less amount of 

 magnesia, and a larger amount of iron, and appear all to pos- 

 sess the following relations as regards the oxygen, 3:3:4:3. 



According to this therefore the Chlorites contain one-third 

 less alumina than the Ripidolites, the quantities of the other 

 elements remaining the same. Both series however are so alike 

 in their properties, that if we suppose alumina to replace 

 silicic acid in the Chlorites in the atomic proportion of 1 : 1, 

 and in the Ripidolites of 3 : 2, a common expression is ob- 

 tained for the two minerals, both then becoming hydrated 

 bisilicates (aluminates). 



* See Phil. Mag. vol. xviii. p. 121, and vol. xxi. p. 76. 



