w.c = 



c:c = 



P:s = 



w:s = 



w:M= 



IV : h = 



n:c = 



^ :c == 



e:c = 



Y:c = 



ff :c = 



w.f = 



P:e = 



S\(p = 



s:f = 



M:e = 



o:b = 



o:c = 



63"22W 

 : 69°24' 

 = 70°47' 

 = 57°54V/2' 

 = 42°24' 

 : 32° 8' 

 = 12^40V2' 

 = 24°13V2' 

 = 41°59' 

 = 60°56V2' 

 = 74°28^''2' 

 = 77°253/4' 

 = 51°45V2' 

 = 70°44' 

 ■■ 45°20' 

 = 67°59' 

 : 69°27V4' 

 = 38°463/4' 



o -.(p- 

 o:e = 

 o:f- 

 i:b- 

 n : Ъ = 

 'u:e -- 

 x:(p- 

 у.Ъ-. 

 C.b- 

 k:b-- 

 k:(p- 

 k:w- 

 s:b- 

 e.M- 

 e:C- 

 m : h ■- 

 m : к = 

 ^:£ = 



= (111) 

 = (111) 

 = (111) 



= (121) 

 = (131) 

 = (131) 

 = (211) 

 = (311) 

 = (331) 

 = (411) 

 = (411) 

 = (411) 

 = (431) 

 = (431) 

 = (431: 

 = (621) 

 = (621) 



= (63i: 



(Oil) 

 (021)^ 

 :(041)^ 

 :(010) 

 :(010) 

 :(021) 

 :(011) 

 :(010) 

 :(010) 

 :(010) 

 :(0П) 

 :(301) 

 :(010) 

 :(110) 

 :(331) 

 :(210) 

 :(411) 

 :(431) 



ЗГ14' 



35°28^/4' 

 46°44' 

 53° 9V2' 

 41°39V2' 

 24°20' 

 50° 19=^/4' 

 78°36' 

 58°50' 

 81° О' 

 67°35=^/4' 

 10°48V2' 

 64°35V2' 

 19°49=*/4' 

 ■ 7°49V2' 

 14°57V2' 

 7°14V2' 

 : 9°26V2' 



Etching figures. 



We do not find many minerals showing so good conditions 

 for the formation of etching figures as the ilvaite. Not only is 

 the mineral very easily corroded by acids whereby rather well- 

 developed etching figures are formed : but such figures are 

 also produced by alkalies, although to a far smaller degree; and 

 finally may also be found natural etching figures, deviating from 

 both the preceding types, and in some respects occupying an 

 intermediate position between those types. 



As the vicinal faces in the ilvaite, as before mentioned, 

 sometimes would seem to form a monoclinic whole, it was an 

 obvious conclusion to try to use the etching figures for the 

 determination of the form of the crystal ; these figures, how- 

 ever, decidedly imply that the mineral is rhombic. 



