HO. 2346 CONTRIBUTIONS TO MINERALOGY— SHANNON. 451 



scopic inclusions. The extinction is parallel and elongation posi- 

 tive. Indices of refraction, roughly maximum, 1.635; minimum, 

 1.629. An analysis yielded : 



Analysis of bucholzite from Blandford, Massachusetts. 



SiOi 38.10 



AlaOa 59.48 



Fe^Os 1. 05 



Ignition 1. 32 



Total 99. 95 



It seems unquestionable that the sillimanite is derived from por- 

 tions of the highly aluminous schist absorbed by the pegmatite ma- 

 terials in their upward progress. A noteworthy fact is that in this 

 general vicinity the schist contains veins of coarse granular quartz 

 with small amounts of muscovite and black tourmaline and abundant 

 cyanite. These veins may well represent a phase of the pegmatite 

 intrusion, the compound AljSiOg taking the orthorhombic form of 

 sillimanite at a higher temperature, and assuming the triclinic form 

 of cyanite where the temperature was below the inversion point. 



STILPNOMELANE FROM NEW JERSEY. 



In 1899 F. W. Clarke^ described, as a new hydromica, a mineral 

 collected by N. H. Darton in a trap quarry at Rocky Hill, N. J. 

 The material is described as in minute flakes thinly matted together; 

 color, a golden bronze with some portions slightly greenish ; soft and 

 thinly foliated; under the microscope exhibits no definite crystal 

 form, and its optical properties, while not distinctive, suggest biotite. 

 It is apparently biaxial, with a very small axial angle, and is pleo- 

 chroic. Heated it does not exfoliate, but fuses to a dark-colored 

 bead. DecomiJosed readily by hydrochloric acid. 



Specimens preserved in the described material of the United States 

 National Museum (Cat. 84735-84736), as the type of this mineral are 

 not the original material, but were received from Washington A. 

 Roebling, of Trenton, New Jersey. The specimens bear the original 

 label in Roebling's handwriting, with the following inscription: 



Clarke's new hydromica ; see page 71 Dana's App., under vermiculite. Ihe 

 result of the alteration of diabase (precisely how is this accomplished?) from 

 Barber Ireland's Trap Quarry, Lambertville, N. J. 



The specimens attracted the attention of the present writer by 

 reason of their remarkable resemblance to the stilpnomelane and 

 chalcodite recently described from Westfield, Massachusetts ;2 and 



» Clarke, F. W., and Darton, N. H. On a hydromica from New Jersey, Amer. Joum, 

 Sd., vol. 7, p. 365, 1899. 



» Shannon, E, V. Diabanlite, Stilpnomelane, and Chalcodite of Westfleld, Massachu- 

 setts, Proc. U. S. Nat. Mus., vol. 57, p. 397. 



