NO. 2348. MINERALS FROM TRUMBULL, CONNECTICUT— SHANNON. 473 



CRONSTEDTITE. 



Cronstedtite has been reported from here,^ but none was seen by 

 the writer. No data as to its mode or phice of occurrence are given, 

 and until the mineral has been examined chemically or optically its 

 identity with cronstedtite must remain in doubt. 



DIASPORE. 



Diaspore is mentioned as coming from here in Dana's Mineralogy, 

 and it is to be expected in the topaz veins, although none was seen 

 by the writer. 



PROCHLORITE. 



A careful search was made of all the openings in the hope of 

 finding cronstedtite, which has been reported from here. Nothing 

 comparable with this ferric chlorite was found, but there were noted, 

 in joints in marble in the bottom of the main pit, some narrow veins 

 filled with a greenish black chlorite, which formed fine granular 

 friable aggregates of small variously oriented crystals. Where free 

 surfaces are present the chlorite exhibits the vermiform curved pris- 

 matic crystals commonly called helminthe forms. These free sur- 

 faces are usually coated with manganese oxide. The granular 

 aggregates look entirely like the prochlorite from the District of 

 Columbia.^ 



Upon analysis the mineral was found to have the composition 

 given in Column I below. In Column II are given the results ob- 

 tained by Clarke upon the chlorite from the District of Columbia 

 described by Merrill. 



Anali/scs of prochlorite from TruDitnll and W'tsltitigtmi. 



Aside from the water content, which is a little low, the composi- 

 tion of the Trumbull chlorite approaches the average of available 



» Hoadley, Chas. W., An American Occurrence of Cronstedtite. Amer. Min., vol. 3, 

 p. 6, 1918. 



2 Merrill, G. P., Proc. U. S. Nat. Mus., vol. 7, p. 67. 1884. 



