PALACHE AND WOOD. — CRYSTALLOGRAPHIC NOTES. 649 



Magnetite. Magnetite in crystals more or less perfect is frequently 

 found in veins in the emery. In our specimens we find it most often 

 with dark green corundophyllite crystals and with the sapphire corun- 

 dum, diaspore and rutile being present occasionally. 



The crystals are of two habits : 1, simple octahedrons, often quite 

 large, showing excellent octahedral parting ; 2, dodecahedrons with 

 slight modification by octahedral planes, faces of the former always 

 striated parallel to the longer diagonal of its faces, the latter bright. 

 Tiny crystals of the second habit, embedded in amethystine diaspore, 

 have the symmetrical perfection of a model. 



Rutile. As stated by Emerson rutile was abundantly formed, follow- 

 ing corundophyllite and diaspore, chiefly in the form of acicular and 

 sagenitic growths. These are generally imbedded in calcite. Our ma- 

 terial presents abundant illustrations of such growths, the dull to bright 

 red needles showing every variety of sagenitic network and of cyclic 

 and repeated twinning, the groups minute for the most part and very 

 beautiful as examined under high magnification, as with the Zeiss stere- 

 oscopic microscope. Much of the sagenitic rutile is apparently in the 

 form of ilmenite plates, which have been altered to rutile and magnetite. 



Occasionally crystals of rutile of stouter proportions are revealed in 

 cavities from which calcite has been removed by acid. One such crystal 

 which was measured showed a prism zone deeply striated by oscillatory 

 combination of the forms, a (100) and m (110) ; the terminal forms com- 

 prised e (101), s (111), and g(212), the latter and other uncertain dite- 

 tragonal pyramids forming a striated zone between e and s. 



Cobaltite. This uncommon mineral was found on a number of speci- 

 mens collected by us at the emery mine in 1903. It has not been 

 hitherto described from the locality, and this seems indeed to be the first 

 established occurrence of the mineral in the United States. 



It occurs in well-formed cubical crystals up to 2 mm. on an edge and 

 in irregular masses surrounded by chalcopyrite. The crystals are bril- 

 liant, silver white in color, and show the cube, a (100), octahedron 

 p (111), and pyritohedron e (210), the cube generally dominant. A few 

 crystals, however, show pyritohedral outline, the faces deeply striated, and 

 on this type the octahedron is lacking. Crystals with octahedron domi- 

 nant were not seen. The free crystals, revealed by removing with acid 

 the enclosing calcite, are implanted on acicular diaspore or on the pale- 

 green amesite variety of chlorite ; associated with them are magnetite, 

 ilmenite, rutile, and chalcopyrite, all in distinct crystals. The massive 

 cobaltite surrounded by rims of chalcopyrite occurs in the same veins 

 with the crystals, in parts where it was not so free to develop. The 

 veins in which it occurs are always bordered by comparatively thick 



