Dr. Blum on Pseudomorphous Minerals. 77 



serpentine ; and also that crystals of olivine of the size of these 

 crystals of serpentine had not been observed. Other reasons are 

 brought forward by him for doubting (iuenstedt's view, but 

 they appear unsatisfactory. Breithaupt has long since suggested 

 that serpentine may be an altered hornblende rock or Diorite ; 

 beds of Diorite in Saxon Voigtland sometimes have the characters 

 of serpentine, and there is good reason for believing that all serpen- 

 tine, as well as its contained minerals, is actually of metamorphic 

 origin. The occurrence of so many pseudomorphs consisting of 

 steatite, an allied mineral, favors this view. The exact imitation 

 of olivine in these serpentine crystals, and their rounded forms 

 and dull lustre, leave little doubt that they are actually altered 

 crystals. Besides, instances of olivine altered to a greenish or 

 brownish yellow steatitic mineral, have been described by Reuss 

 as occurring in Bohemia and elsewhere. 



Hornblende with the form of Augite. — The Uralite of Rose, 

 a mineral with the form of hornblende and cleavage of augite. Dr. 

 Blum shows to be an altered hornblende. He mentions various 

 instances of the singular mixture or union of the two minerals, 

 which he explains by supposing this change to have been partially 

 carried out. He describes druses of crystals from Arendal, Nor- 

 way, which have the form of hornblende, but nothing of its tex- 

 ture within, and which he concludes therefore to be pseudo- 

 morphs of hornblende. Other examples of this kind of pseudo- 

 morph are said to occur in porphyry near Miask, near Predazzo 

 in the Tyrol, at Mysore in Hindostan, and elsewhere. Dr. Blum 

 also mentions a greenish white augite from Orange County, N. Y. 

 in the Leonhard collections, which he supposes to have under- 

 gone the same change from hornblende. This is indicated both 

 by its structure and angles. 



The metamorphosis in the composition producing this change 

 is in general an increase of the bases. The varieties of the two 

 minerals differ so much that it becomes difficult to represent the 

 change by means of the formulas. 



Chlorite with the form of Garnet. — This pseudomorph in do- 

 decahedrons has been observed in Saxony associated with granular 

 limestone ; also near Frammont and near Berggieshiibel. 



From Ca^' Si+Fe Si (garnet) remove 3Ca, Pe, and add to the 



same 3(Mg, Fe), Al, 2MgH% and the new substance (chlorite) 



is obtained (Mg, Fe)^ Si+Al Si-f 2Mg K». 



