132 



MINERALOGY 



Brachy series of prisms, 

 Macro series of domes, 

 Brachy series of domes, 



n : b : ooc, (hko). 

 n& : b : oo c, (hko) . 



na: oob: me, (hoi). 

 na : oo b : me, (hoi) . 



f oo a : nb : me, (ohl). 

 I oo a : nb : me, (ohl). 



Fig. 261 

 Fig. 262. 



Macropinacoid, &: oob: ooc, (100). 



Brachypinacoid, oo a : b_: oo c, (010). 



Basal pinacoid, ooa : oob : 6, (001), Fig. 263. 



Examples. The plagioclase feldspars crystallize in this type. 

 Fig. 264 represents a combination ofJUO) (110) (100) (111) 

 (201) on a crystal of axinite, in which & : b : c = .492 + : 1 : .479 + and 

 a = 82 54', p = 91, \ = 131 32', 100 A 010 = 48 21'. 



Fig. 265 is the combination of the three pinacoids in rhodonite, 

 MnSi0 3 , in which a = 103 18', p = 108 44', -y = 81 39'. 



CLASS, TRICLINIC HEMIMORPHIC 

 TYPE 1, ASYMMETRIC 



Symmetry. Crystals of this type possess no symmetry what- 

 ever, and each form of the type is composed of a single face, Fig. 



266. Any collection of faces, how- 

 .."'" '***-. ever irregularly 



grouped, may 

 belong to this 

 type, provided 

 they conform to 

 the law of ra- 

 tional indices. 



All forms of 

 the type may 

 be considered as 

 being produced 



by the selection of one face of the pair form- FlG ^_ CalciumThio _ 

 ing the corresponding holohedron of type 2. 

 Forms. Possible forms will be the same 

 as in type 2, except they will all be hemi 



FIG. 266. Type 1, Asymmetric. 



sulphate : Combinations 

 ofc(001),b(010),m(lTO), 

 q(011), andh(llO). 



forms consisting of one face each, and designated as the upper 

 right front hemipyramid, or as the lower back hemimacrodome, etc. 



