

i 



Mineralogical Notices. 389 



The second is the mean of three analyses. 



The augite gives for the oxygen of the silica, aUimina and 

 protoxyds, 24-69 : 379 : 13 27; and for the oxygen of the sih'ca 

 and alumina together 28-48. 28 '48 : 13-27 = 1 ; 2-15, The ratio 

 does not become 1 : 2 except we suppose 23:1 to replace i5i. 



The hornblende affords in like manner 2209 : 5-14 : 13-29, 

 and for the oxygen of the silica and alumina 27-23. 27'23 : 13-29 



1 : 2-05. 



The augite has nearly the ratio usually given for hornblende. 

 4:9; while the hornblende has the augite ratio 1:2. So the Ta- 

 berg black augite affords the hornblende ratio 1:2-39=4: 9*5, Ram- 

 melsberg hence shows that hornblende does not consist uniformly 

 of ifisi with iS^Si^ the usual formula; but that both it and au- 

 gite may be a pure bisilicatej k^ Si% or may correspond to the 

 general formula, mBsi+tifi^ gi^^ |q which m and 7i may be each 



a unit, or 3 and 2, or other numbers, the addition of m atoms of 

 the trisilicate to n atoms of the bisihcatCj producing no change 

 of form. The ratio 4 : 9'33 which is common in hornblende, 

 woj.ild give for m, ii^ the values 3, 2, and afford the formula 

 sSSi+2fi3Si% equivalent to K^ Si^. This formula corresponds to 

 the analyses of a tremoUte from Fahlun, an actinolite from Ta- 

 berg, a hornblende from Helsingfors, each containing no alumina ; 

 and of the aluminous varieties from Kongsberg, Kimito, La Prese, 

 Lindbo, Vogelsberg, Bohemia, the Uralite, &c. 



M. P. Sandberger (on p. 453 of the Ixxxiii volume o^ Poggen- 

 dorffj) precedes the paper by Rammelsberg by mentioning many 

 cases of the close intermixture of hornblende and augite crystals, 

 and describes cases of twins in which one part of the crystal is 

 augite and the other hornblende. He also describes crystals of 

 augite containing throughout particles of chrysolite, the latter 

 niineral being in parallel combination with the former. In other 

 specimens he finds hornblende and chabasite intimately mingled- 

 This combination of hornblende and augite in a single twin 

 Would seem to show that the difference between them is not due 

 to temperature. M. Sandberger urges that the hornblende and 

 augite in tlie cases adduced cannot be either one or the other a 

 result of pseudomorphism, and that both are properly the same 

 tniiieral species. 



Rutile of Waterbury, Vermmit— Dr. A. A. Hayes in remark- 

 ing on a specimen of quartz containing acicular rutile from Wa- 

 terbury, Vermont, before the Boston Society o( Natural History, 

 (Proceedings, 1851, 23,) stated that the acicular crystals must 

 have existed occupying a cavity before the quartz was formed. 

 The rutile needles often pass through the regular terminations of 

 the quartz crystals, and roughen the surfaces by their broken 

 ^nds. The flaws or rents in the mass of the crystal are most 

 frequent about the rutile, indicating that this mineral by its 



Second Seeies. VoL XIL No. 36.— Not^ 1851. 60 



