488 G. H. Williams—Cleavage in American Sphene. 
Rose. Des Cloizeaux. Dana. 
Po (y) oP (p) oP (0) 
2P2 (rn) -P (dd) _2P (2) 
4Pi— (n) ~2P (d*) —4P (4) 
ete sc fr) oP (m) ok 2{f) 
—2P2  (t) P (8) oP (—2) 
The face 7 is not common. It has been obser tet ae Des 
Cloizeaux on greenovite, the manganese sphene from St. arcel, 
Piedmont,* and by Hessenberg on crystals from Pfitsch in 
Switzerland.+ It is also present on several crystals of the 
lederite habit in my possession, occurring with apatite in a red 
calcite near Eganville, Renfrew Co., Canada. This face lies 1 
the zone y:r and makes with y an angle of 130° 27’—(calcu- 
lated 180° 45’ (Des Cl.)). In one of the crystals showing this 
plane the parting is exceptionally well developed ; and the 
simultaneous reflections from both the crystal plane and part: 
se Pe dei shows that they are exactly parallel. : 
he most perfect development of this parting which I have 
anywhere observed is in the silvyery-brown sphene, associate 
with the white microcline and green malacolite from Pitcairn, 5+ 
Lawrence Co., N. Y. ese minerals are found imbedded in 
a coarse grained calcite and all have their faces and angles so 
rounded that accurate crystallographic determinations are very 
difficult. The malacolite shows a perfect parting parallel to 
OP. In the sphene the parting is, as a rule, much more per 
fectly developed parallel to one pyramid face than it is parallel 
to the other. After a number of trials such pieces were 
obtained as gave equally distinct reflections from both surfaces 
and the angle between them was determined by measurement 
to be 125° 26’. The calculated angle, as given by 1° 
* Manuel de Min., i, pl. xli, fig. 245. 1862. 
+ Mineral. Notizen, No. 4, p. 18, figs. 14, 15, 18, 19. 1861. 
