.NO. 2348. MINERALS FROM TRUMBULL, CONNECTICUT— SHANNON. 477 



Although the total iron is low, the angles agree very well with 

 those of normal epidote, showing but little approach to the clinozoi- 

 site ratios. The forms positively identified on several crystals meas- 

 ured are given below : 



./- 



Several forms Avere noted on single crystals which could not be 

 identified, but unless the readings 

 are unusually dependable the ori- 

 entation of unterminated crystals 

 is very difficult. The best termi- 

 nated crystal is shown in figure 1. 

 The angles obtained upon this 

 crystal are compared with those 

 given for epidote by Dana in the following table : 



Measured and calculated anf/Jes of epidote. 



Fig. 1. — Clinographic projection op a 

 crystal of epidote. 



r A a =(001) A (100). 



c M =(001) A (102). 



c As =(00nA(203). 



(■ Ar =(001) A (101). 



c A I =(001) A (201). 



c A/" =(noi)A(:-'-Oi). 



a Ao =(100)A(0n'i. 



a' A 71 =(100) A (111) 

 n An^^'=rill)A(lll) 



CA 36 



34 20 



45 2 



63 49 



89 4 



99 19 



77 15 



09 20 



70 13 



C4 36 50 



34 21 00 



45 37 00 



63 42 00 



89 26 00 



98 37 00 



77 2 30 



69 2 00 



Before the blowpipe the mineral turns dark brown and fuses to a 

 dark-brown bead which is not magnetic; yields strongly acid water 

 in the closed tube; under the microscope is transparent fragments 

 having a faintly brown color which is not pleochroic and is probably 

 due to dispersion by submicroscopic inclusions. The fragments 

 under the microscope show a very well-defined cleavage, probably 

 parallel to the basal pinacoid, c(OOl). The indices of refraction as 

 determined by immersion claim no great accuracy, as the series of im- 

 mersion media had rather wide intervals in this range and the values 

 given are approximated by interpolation. The figures arrived at are : 



ci=l. 706i!r.003 



/3=1. 710±.003 



7=1. 720±.003 



o-7= .014±.003 



