63 



found in a single crystal, and are very small , but give rather 

 good reflexes. С{33|} and ?!^{63l} are determined by lying in 

 the zone (431 :431) and by the angles: 



Measured Number of Calculated 

 value measurements value 



с : (7 = (431): (331) = 7° 57' 1 7° 49V2' 



£:*y --= (431): (631) = 9° 15' i 9° 26V2'. 



г{401} is determined by lying in the zones (101 :001) and 

 (431 : 431), and further by the angles 



Measured Number of Calculated 

 value measurements value 



i:e = (401): (431) = 25° Г 1 25° 24V2' 



г: с = (401): (001) = 69° 37' I 69° 24'. 



The most characteristic feature of all the crystals is the 

 high development of £(431); otherwise the other faces, which 

 are always, excepting the faces of the prismatic zone, very 

 small, may be rather differently developed, and more or fewer 

 may be wanting. All the crystals have very bright and shining 

 faces, all, excepting £{43l}, giving very 

 good reflexes. 



Type X. 



To this belongs a rather large number 

 of crystals, showing in the details rather 

 great variations. The largest (1 — 2°") and 

 most characteristic ones have the appear- 

 ance shown in the figure. 



Combination: b{o\0], d{iw], s{l20}, ^- 

 Ж{110}, фю}, n[0\2}, P{lOl}, ojlll}, 

 ж{211}, C{33l}, £{431}. 



The prismatic faces are perpendicu- 

 larly striated to a very high degree; the 

 other faces are generally rather dull, which, 

 I think, may be due to the fact, that the 

 calcite that has originally surrounded them, 

 is resolved. Fig- и. Ilvaite, type X. 



