1873.] OaO [Genth. 



species except rutile and quartz owe their existence to the former pres- 

 ence and subsequent alterations of corundum. 



The same is in all probability true with reference to the occurrences of 

 pyrophyllite, both radiated, stellate, and the slaty in Montgomery, 

 Randolph, Moore, Chatham, and Orange Counties of North Carolina, 

 and perhaps Chesterfield District, South Carolina. 



14. Staurolite. 

 With the damourite, resulting from the alteration of corundum at the 

 Culsagee Mine, are found very few and minute brown grains of subvitre- 

 ous lustre ; the grains are massive and of irregular shape and do not 

 show a trace of a crystalline form. Their spec. grav. was found to be 

 = 3.711, and the analysis showed them to be staurolite. It gave : 



contains oxygen 14.49 



24.74 

 2.06 



} 



1.73 ) 

 1.31 ) 



26.80 

 3.04 



100.37 



The oxygen ratio 3.04 : 26.80 : 14.49 is = 1 : 8.8 : 4.8 

 or near 1:9:5 giving the formula 2RO, SiO;, -f- 2 (3A1A> 

 2Si0 2 ). 



15. Pyrophyllite. 



In his " Chemical and mineralogical relations of the metamorphic 

 rocks," T. S. Hunt* says : " The last term in this exhaustive process 

 appears to be represented by the disthene {cyanite) and pyrophyllite rocks, 

 which occur in some regions of crystalline rocks.'''' 



I suggested under the heading "cyanite " that the pyrophyllite found 

 in several of the Counties of North Carolina, South Carolina and Geor- 

 gia, is the result of the alteration of the former, perhaps, from A1 2 3 , 

 SiO, into AlA, 3 Si0 2 + H 2 0. 



This view is sustained by pseudomorphs of pyrophyllite in the form of 

 cyanite from Villa Rica, in Brazil, described by F. Sandberger.f 



An association very similar to that at Crowder's Mountain, North 

 Carolina and elsewhere, viz. : cyanite, pyrophyllite, damourite, hematite, 

 andlazulite, occurs at Horrsjoberg, in the District of Elfsdalen, in rutile 

 Wermland and Westana in Sweden. That these were formed under 

 similar circumstances cannot be doubted. 



Several other hydrous aluminous minerals have been found in associa- 

 tion with corundum or with minerals which are the product of its altera- 

 tion ; for example, those accompanying the beauxite in the southern 



»T. S. Hunt, Sill, Joum . [2] XXXVI, 222. 



t F. Sandberger, Leonhard— Broon's Jahrbuch der Mineralogie, 1855, 315. 



