ith and Penfieldr — Lansfordiie^ ffle8quehonite : etc. L38 



The /ones and the approximate measurement of tbe angles 



fully determine the forms on this crystal. The dome <\ which 



is relatively quite a large face, is reduced almost to a line in 

 our projection. 



No. ne of the most perfect of the stalactites ; it is short, 



10 ,um long and (')""" in diameter. At the base the white material 

 of the altered lansfordite spreads out verv much and covers a 

 group of nesquehonite prisms which are attached to a piece of 

 carbonaceous shale. The planes which are present are very 

 symmetrically grouped, reminding one of a monoclinic crystal, 

 and are as follows: />. 010; <\ 001 ; M 1U> and HO; <L 021; e, 

 051 ; ./■. 123; //, HI ; j>. Ill and /\ ls~2. The arrangement of 

 the faces in about their natural development is shown in fig. 9, 

 while fig. 10, which is a projection on a plane at right angles 

 to the vertical axis, will give a somewhat better idea of the 



q metrical arrangement of the faces. The large basal plane 

 c is in two levels, and to the left there is a cleft in the stalac- 

 tite which is also bounded by crystal faces, not shown in the 

 drawing. The faces of the crystal were quite devoid of luster 

 before rubbing and polishing with a soft cloth, by which treat- 

 ment the edges were somewhat rounded and the angles of the 

 faces slightly changed ; however, the faces can be fully deter- 

 mined by the zones and the approximate measurements. The 

 angles measured in the prominent zones are as follows: 



&aM. 010 aI10 = 64 

 6 a d, 010 a 021=39 

 d> c. 021 a 001=45 

 ca e, 001 a 021=49 

 Pa r, 111 a 132=19 

 Ta e, 132 a 021 = 25 



Nos, 9 and 10 are two crystals which had grown together 

 into a single stalactite about 25 mm long by 8 mm diameter, 

 and readily separated lengthwise with the stalactite. At the 

 junction of the two crystals at the lower end there was a deep 

 reentrant angle, reminding one of a twin crystal but there 

 seemed to be no crystallographic relation between the two 

 halves, and we probably have to do simply with the growth of 

 two crystal- into one stalactite. This much must be said, how- 

 ever, that the axis of the stalactite corresponds closely to the 

 vertical axis of the crystals, and the faces on the two crystals 

 for the most part intersect the negative end of the vertical axis. 

 One of these crystals is represented in fig 11. The rounded 

 surface of the stalactite is behind, while in front there is an 

 angular marking indicating the surface by which the two cry- 

 this were united and at the lower end a group of crystal faces, 

 which are as follow.-: &, 010: c, 001 ; h, L50; m, 110; rf, 021 ; 

 3,021; /•, 125 and j?, ill. The angles were measured in the 





Calculated. 









Calculated 





64° 13' 



d a x, 



021a 132=21° 



10' 



20° 20' 



30 



39 16 



x a y, 



132 a 111=24 



40 



22 50 



10 



44 50 



r a c. 



132 a 001 = 41 



25 



43 24 





51 22 



C A X, 



001 a 132 = 44 



50 



43 52 



54 



21 41 



M a v. 



.10 a 111=43 



30 



44 10 



24 



24 36 



7/aC. 



111 ~ 001=53 



30 



52 25 



