alcn 



lated. 







Calculated. 



64° 



13' 



b*d, 010 a 021=39° 



5' 



39° 16' 



56 



57 



d^c, 02J a 001=44 



50 



44 50 



21 



41 



c^e, 001 a021 = 51 



5 



51 22 



24 



36 



r~c, 122 a 001=44 

 c^x, 001a 112=42 



5 



43 24 

 43 52 



134 Genth and Penfield — Lansfordite^ Nesquehonite, etc. 



following zones : £>, h and in ; p,r, e and m and d, b, e and e ; 

 and are as follows : 



Calculated. Calculated. 



b Am, 010 a 110=56° 47' 58° 50' d~ 6, 021 a 010=38° 55' 39° 16' 



h Am, 150^110=39 11 39 31 b a e, 010 a 021=45 44 32 



^ a r, 111 a 132 = 21 31 21 41 e ~ c, 021 a 001 = 50 50 51 22 

 r* e, 132 a 021=24 9 24 36 



The other half of this stalactite is shown in fig. 12, where 

 the rounded stalactitic surface is in front, while the small group 

 of crystal faces, which are mostly in the back, are indicated by 

 dotted lines. The forms which were identified are as follows : 

 M, 110 ; m, 110 ; c, 001 ; b, 010 ; d, 0§I ; e, 021 ; p, III.; r, I3§ 

 and a?, 132 ? and were measured in the following zones : b 7 M 

 and m, ^?, r and <? ; J, 6?, c and ; and r, e and a?, the angles 

 being as follows : 



&aM, 010 a 110=64° 10' 

 MaW, 110a110 = 57 15 

 |)a r, 111 a 132=21 30 



r* e, 132 a 021=24 25 



No. 11 is a small stalactite 18 mm long by 7 mm diameter, which 

 when it was first sent to New Haven in the spring of 1889, 

 still showed the paraffine luster of the unaltered lansf ordite; when 

 it was measured in the following fall it was only partially altered 

 to nesquehonite, but had become almost completely changed by 

 the first of December. The faces did not give good reflections 

 of light, but as the angles which were measured on this partially 

 altered crystal do not vary widely from the calculated, which 

 were obtained from the measurement of a completely altered 

 crystal, we conclude that in the change of composition the 

 angles of the lansfordite have not been very materially changed. 

 The faces which were identified are as follows : b, 010 ; c, 10 1 ; 

 m, 100 ; M, 110 ; p, ill ; d, 021 ; and P, III, x, I32, and are 

 arranged as shown in fig. 13. The angles were measured in 

 the following zones : &, m and M ; m, c and P ; and m, x and 

 d, and are as follows : 



Calculated. Calculated. 



b a w, 010 a 110=59° 15' 58° 50' ra a c, 110 a 001=103° 30' 101° 48' 



m a M, 110 a 110 = 58 56 57 c a P, 001 a 11_= 44 30 43 15 



<Za x, 021 a 132 = 19 20 20 c a p, 001 a .11= 44 30 44 59 



This is the only crystal on which the pyramid P, 111 was 

 identified, and here it occurs only as a very small face whicji 

 is not represented in the drawing. It is interesting to find on 

 the mineral all of the four possible faces making up the tri- 

 clinic unit pyramid. On this crystal we notice that the decom- 

 position or change from lansfordite to nesquehonite proceeds 

 along certain planes which are parallel to the base. It is proba- 

 ble that these planes indicate the direction of cleavage of the 



