170 The Monoclinic Pyroxenes of New York State. 



6,10 mm. in diameter respectively. The temperature at which 



the measurements were made was 15.25°-25.75° C. 



a 1.6674 



|8 1.6745 



A 1.6961 



2 V = 60° 18' 



2 E = 114° 29' 



Direct measurement of the optic axes in Na light gave : 

 2 E = 114° 3' 22° C. 



2 H = 60° 46' 



2 H = 122° 9' 



The indices of refraction as determined by Zimanyi are still 

 lower than those of Ala, which Des Cloiseaux (Man. Min. 1862, 1 

 p. 55), Dufet, Bull. Fr. Min. Soc, 1887, X, p. 290, Wulfing and 

 Schmidt, Zeitschr, fur. Krystu. Min. 1893, XXI. 



Udenville, Orange Go — Rammelsberg gives in his Mineral- 

 chemie (Ref. 37), an analysis of a large bluish crystal from Eden- 

 ville, which is as follows : 



Percentage. Ratio. Prop, parts. 



SiOj 55.01 .917 13 



FeO 4.95 .099 1 



CaO .22.80 .407 6 



MgO 16.95 .424 6 



H2O .36 



100.07 

 Sp. Gr. 3.94. 



The above analysis calculated out gives CagMggFeSijgOgg 

 which corresponds pretty closely to the formula Ca Mg SigOg. 



Edwards, St. Lawrence Co. — The only specimens which the 

 writer has seen from this locality are some crystals in the col- 

 lection of Prof. Egleston. They are of simple habit and the com- 

 bination of forms is a (100) and 6(010) broad, 7n(110) narrow 

 li(lll) and c (001). The faces have altered to tremolite. 



Macomb St. Lawrence Co. — There is one group of small glassy 

 crystals in the Columbia University collection. The crystals are 

 tabular parallel to 6(010) and have the faces a (100), 6(010), 

 m(llO) c ('OOl)and it (111). The associated minerals are albite, 

 calcite and graphite. 



Pierrepont, St. Lawrence Go. — Transparent crystals tabular 

 parallel to 6 (010) are common. They occur mostly as small 

 groups of interlacing crystals. Basal and orthopinacoidal twin- 



