AZURITE CRYSTALS FROM MINERAL HILL. 281 



developed than in the crystals of Habit I, and w (120) is 

 here usually a small triangular face. The orthodorae v (201) 

 is, as before, strongly striated parallel to its intersection 

 with a (100). The "no man's land " between c (001) and 



(101) is in some' cases of considerable breadth and has a 

 strong influence on the general shape of the crystal [Plate 

 VI, figs. 1, 2]. It is gently curved, finely striated, and 

 gives a regular succession of signal reflections in the tele- 

 scope; readings were obtained from dominant reflections 

 which indicate the presence of ^ (105), D (104), F (207) and 

 A (l03); of these D is the most probable and it is included 

 in fig. 4. The three clinodomes I (023), f (011), and p (021), 

 are well developed and smooth, particularly I and f , though 



1 is sometimes slightly striated parallel to the zone edge. 

 Of the pyramids, h (221), k (221), and .R(241) are the most 

 prominent as before. The new form X (481) was observed 

 on two crystals, s (111) and P (223) each on four and 

 usually simultaneously; y (121) was found twice as a narrow 

 face between m (110) and f (011). The pyramid A (2*18*3) 

 is never present on the crystals of this habit. 



Elements. 

 The elements of azurite are in a curious position. Those 

 adopted in standard works, such as Dana's 'System of 

 Mineralogy,' Groth's 'Ohemische Krystallographie,' Gold- 

 schmidt's 'Index der Krystallformen' and 'Winkeltabellen,' 

 were determined by Schrauf from measurements on the 

 azurite from the well-known locality Ohessy in France, 

 although the later authors have generally taken half the 

 length of the vertical axis chosen by Schrauf. Schrauf's 

 classic paper 1 was published in 1871 and most crystallo- 

 graphers who have since measured the angles of azurite 

 from other localities have found marked discrepancies 

 between the values obtained and those calculated from 



1 Schrauf, Sitz. d. k. Akad. Wiss. Wien, lxiv, 1871, abth. 1, pp. 123 - 136. 



