G. H. Williams—Oleavage in American Sphene. 487 
fundamental rhombohedron is well known in corundum and 
hematite crystals from many localities. 
uring his recent visit to this country, Professor vom Rath 
suggested to the writer that the apparently perfect cleavage so 
often observed in the American sphene might be due to pre- 
cisely the same cause, and such indeed upon investigation 
turns out to be the fac 
sphene from Smaland, Sweden, recently named by him alshe- 
ite. 
The sphene which occurs so abundantly in this country 
associated with various silicates or with apatite in the lime- 
stones of the Laurentian, is almost always of a chocolate-brown 
color, and shows when in distinct crystals the habit of the variety 
called by Shepard lederite, (see figure). Whenever anything 
resembling a cleavage is present, the surfaces meet under the 
angle given above, corresponding to that of the pyramid —4P 
(according to Dana). This is, however, not a true cleavage but 
a parting caused by repeated twinning, as in the case of salite. 
That the exact position of these lamelle may be better 
understood, a figure of a crystal of the lederite type is here 
given with the following table of the different symbols assigned 
to the planes by G. Rose,§ Des Cloizeaux,| and Professor J. D. 
Dana.4 | 
* This Journal, I, xxxix, p. 357. 1840. 
+ Handbuch der Mineralogie, 3d ed, p. 440. 1877. 
yst. Min., II Appendix, p. 122. ' 
De Sphenis, e ‘ oe teal Berlin, 1820. 
Manuel de Min., i, p. z. ‘ 
Syat, Min, bth’ ed. p. 384, (The signs of the hemipyramids are changed 
to accord with general usage.) : 
