NO. 1 148. TO I' A Z CR 1 's TA LS I X Til E X t Tl oX.IL M USE UM-EA KLK. 



367 



l''l(l. n.--T<)l'A/, OinSI'AL I'lioM I'IKIOS 

 I'KAK, (,'<)l.()UAlin. 



Fig. 16 is ;i simpler coinbination than (lie precoding, but is iiiaikcd 

 by the steep inacrodoine /j |401 1 not sliown in the drawing. (No. 50(Ki7, 

 U.S.N.M.) 



ZACATECAS AND DURANGO. 



Tiie crystals from tliese two localities are so similar to those from 

 San Luis I'otosi that no separate descri[)tion of them is necessary. ()u 

 one of the Zacatecas crystals a face of the rare prism M |230| occurs. 



I'IKKS I'EAK. 



The collection embraces some fourteen crystals and ])ie('es from this 

 region. They range irom 2 to 5 cm. wide 

 and, unlike most of the crystals heretofore 

 described, they show double terminations. 

 They are colorless or of a faint bluish tint, 

 and some are stained yellowish. All an; 

 of the same habit, and quite similar to the 

 ]lmen mountain crystals. Cross an<l 11 il 

 lebrand' reported the occurrence of t<)i)a/, 

 from this locality, citing the observed 

 forms, two of which |445| and 142 1 ap- 

 pear (questionable. Later lie v. K. T. Cross- 

 mentions those found in the Platte mountains and gives the forms, 

 all common, except |332(. These three forms mentioned do not 



occur on any of the crystals examined, 

 but, on the other liand, there are seven 

 foruis present not mentioned in their 

 descriptions. 



These are u |111|, x {243j, X |043|, 



h JOlOi, (T/ |130|, i¥ 1 230 1, and J 1 0.10.9 j. 



Ol" these X is common and characteristic 



and the renuiinder, Avith the exception of 



?f, are of rarer occurrence. The form J 



is denoted by one face lying in the two 



zones (111) (043) and (223) (OTO), and its 



indices were calculated from these /ones, 



as the face is too rounded for good 



measurements. 



Fig. 17 is (juite a characteristic combination for these crystals. No 



base is present, the two faces of A' meeting in a long edge. The dome 



,/■ is large, while y is small. The dome d is also common. (No. S2873, 



U.8.N.M.) 



P^ig. 18 shows a doubly terminated crystal with a richer variety of 

 forms. The brachypyramid x and pmacoid b are rarer forms. 



' Am. Jour. .Sci., 3(1 Bor., XXIV, p. 281. 

 2 Idem, 3(1 Her., XXVI, p. 481. 



Kl(i. IH. 



'I'OI'AZ CKVSIAI. KHOIM I'lKES 

 I'KAK, Coi.OUAUO. 



