100 Moses — Mineralogical Notes. 



yielded double signals. In the second crystal both faces of a 

 yielded a bright and a dull signal, while in the first crystal the 

 two signals were of equal intensity. The results following 

 are derived from the bright signals of the second crystal. 



Crystal 1 showed definitely the forms a (100), c (001), 

 v (101) and h (540), while crystal 2 included in addition the 

 forms t (101) and also two undescribed domes x (102) and the 

 very flat dome y=(l'0*25), but does not include v. Figure 1 

 represents all Jhe faces. The coordinate angles as obtained, 

 after transposition to the conventional position, and the calcu- 

 lated coordinate angles are as follows : 





Measured. 



Calculated. 



Face. 



<t> 



P 



</> P 



c (001) 



90° 



5° 23' 



90° 5°20' 



a (100) 



90 



90 



90 90 



v (101) 



90 



44 46 



90 44 30 



x (102) 



90 



30 27 



90 30 30 



y (1-0-25) 



90 



1 29 



90 7 32| 



t (101) 



90 



38 52 



90 38 31 



h (540) 



48 36' 



90 



48 25 90 



x, y, t and h were very minute faces yielding only faint 

 images. 



These values correspond to the angles 



ac=/3=84°37'. au=45°14'. acc=59°33'. ay=82°3l'. 

 a'*=51°8'. c*=44°15'. M'=82°48'. 



It is to be noted that a change of 3' in the determination of 

 the position of a would almost exactly reduce the values for 

 c, x and y to the calculated values and would lessen the differ- 

 ences for v and t. This amount of divergence was easily pos- 

 sible with the double image. On the other hand, it is to be 

 noted that the angle ac for the isomorphous wollastonite is 

 84° 30', and that for pectolite it has been variously determined 

 as 84° 35',* 84° 30',f 84° 40'j and may be said to be still 

 uncertain. 



(3) New Forms on Atacamite Crystals from Chili. 



Mr. John C. F. Randolph, mining engineer, brought from 

 the Brilladora Mine, Paposo, near the coast in the northern 

 part of the Province of Atacama, several masses of crystals of 

 of atacamite which differ sufficiently from previously examined 

 crystals to warrant description. 



*Greg aud Lettsom, Mineralogy 1858, p. 213. 

 \ DesCloizeaux, Mineralogie 1862, i, p. 541. 

 % Dana, System Mineralogy 1892, p. 373. 



