346 Pal ache and Wood— Cry stallographic Study of Miller ite. 



gates of garnet, pyroxene, calcite and millerite are such that 

 no sequence of formation can be recognized, all appearing 

 rather to have crystallized together. When in the massive 

 garnet the millerite is in grains of small size. On contact sur- 

 faces as developed by removal of calcite with acid, the miller- 

 ite is either in short stout prisms loosely implanted on the 

 garnet and projecting into the calcite with developed terminal 

 planes ; or it is in long and relatively slender striated prisms, 

 which lie parallel to the garnet surface and adhere to it closely, 

 being bent, twisted and contorted in extraordinary fashion as 

 though, after formation, the crystals had been pressed down 



to fit all the irregularities of the uneven underlying surface. 

 Their appearance is unique ; and no explanation of their prob- 

 able mode of formation has occurred to us. So soon as the 

 millerite passes from the immediate contact zone, and is 

 embedded in calcite, the crystals are free from these extreme 

 dislocations ; the long prisms are sometimes warped and 

 knicked by pressure-twinning, but entirely lose the crushed 

 appearance as described above. Crystals may be seen crushed 

 and twisted where they lie prone, but which pass into the 

 calcite and become immediately relatively straight and plane- 

 surfaced. The millerite crystals in the calcite reach dimen- 

 sions quite unusual for this mineral. Prisms two millimeters 

 in diameter and four centimeters long are present among our 

 specimens. They are said to reach a length of eight centi- 

 meters or more (three inches). These prisms are generally 

 sharply trigonal in outline, the three faces bright and polished 



