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jS. L. Penfield — Crystallized Vanadinite. 



Co., Arizona, merit especial attention ; they are small, seldom 

 over l mm in length, of a deep red color, and usually show the 

 very simple combinations mentioned by Mr. Blake. A few 

 highly modified crystals were found possessing pyramidal hemi- 

 hedral forms which are of interest because these forms have 

 rarely been observed in this species and show the close relation 

 in habit between crystals of this mineral and apatite. They 

 possess highly polished faces and are well suited for measure- 

 ment. I have been able to identify the following forms : 



TO, 1010, 1 

 a, 1120, i-2 

 /i, 7T2130, •!(*-!) 

 c, 0001, 

 r, 1012, i 



x, 1011, 1 

 y, 2021, 2 

 v, 1122, 1-2 

 5, 1121, 2-2 

 u, tt2131, ^(3-|) 



The hemihedral forms h and u have previously been observed, 

 the former by C. Vrba* on crystals from Kappel, Carinthia, 

 the latter b}^ M. Webskyf on crystals from Cordoba, Argentine 

 Eepublic. Crystals from Pinal Co. showing these combinations 

 are not uncommon. The most common combination is shown 

 in fig. 1. The pyramid u can frequently be seen on both ends 

 of the crystals, or where the free end shows, can be traced all 

 around the crystals. Of pyramids of the first order x is the 

 most common, but r or y, sometimes both, are frequently 

 associated with it. Of pyramids of the second order s occurs 



frequently, v is seldom met with. Fig. 2 shows the occurrence 

 of these planes which was observed on a single crystal ; fig. 3 is 

 a basal projection of the same. The hemihedral prism h is not 

 common, but I have observed it on a number of crystals ; on 

 one attached by its side I was able to measure it three times on 

 the edges which were available; it was in combination with 

 w, a and c only. From the best measurement, a as (1120^1121) 

 = 35° 6£', the axial ratio a: c = 1 : 0'71121 is obtained. This 

 agrees closely with the ratio given by Schabus,^: 1 : 0*71157, 



* Zeitschr. Kryst., iv, 353. f Zeitschr. Kiyst, v, 512. ^ Pogg. Anu., c, 29?. 



