1 



On the Identity of Eumanite and Brookite. 



39r 



a brilliant bronze, crystallized on three sides, and affords speci- 

 mens much superior to those of the old locality. — Beryls ! The 

 heryls approach nearer to aqua-marines and generally are of a 

 smaller size, and clearer, than those of South Royalston. Those 

 of a sky-blue in the white quartz are very beautiful — Feldspar, 

 In crystals o( the same form as those oi the old locality, large and 

 scarce. These minerals occur in worn granite on the farm of 

 Mr, Solyman Heyward or Heywood. 



L " 



Akt. XLI. — On the Crystallographic Identity of Eumanite and 



f 



Brookite; by J. D. Dana. 



A FEW days since, I received for examination from Mr. X E. 

 Teschemacher of Boston, two minute crystals of the Eumanite of 

 Prof Shepard. They had been long in his cabinet, and were pro- 

 cured from a specimen of the Chesterfield vein, the same locality 

 that alforded the Eumanite. They have the same dark brown 

 color, with a deep brownish red translucence, "like almandine 

 garnet." The hardness, as Mn Teschemacher observed, is about 

 6, or not above 6, scale of Mohs. A comparison of the figures 

 here given will make obvious the identity of the two; figure 1 

 represents Prof, Shepard's crystal, figure 2, Mr, Teschemacher's. 



1. 



2. 



u 



/ 



v-_ 



M 



r' e P 





The latter is only ^Vth of an inch in length, and as no reflec- 

 tion of distinct images could be obser\red on account of its mi- 

 nuteness, I was compelled to adopt the less accurate mode of 

 nieasurement by a reflection of the sun's rays. The result has 

 proved that Eumanite and Brookite are very closely similar, not 

 on^y in physical characters, but also ia crystallization. The^two 

 crystals strikingly difl'er though so nearly alike in form. The 

 lateral planes which are the largest in figure 1, are quite small in 



Second Series, VoL XII, No. 36.— Nov., 1851. 61 



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