320 Spodumene and its Alterations. 



frequent occurrence, mostly in rectangular prismatic masses, up 

 to 18 inches in length, but occasionally in fair crystals, with 

 good terminations, two or three inches long. The predominence 

 of the planes i-i and i-i, commonly results in the development of 

 long square prisms. Its association is very interesting, and will 

 be hereafter described. It was here that the same pseudomor- 

 phous mineral after Spodumene was originally discovered by 

 C. XL Shepard, and announced in 1867, under the name of 

 Cymatolite, by publication in Dana's "System of Mineralogy." 

 His description and partial analysis, and a complete analysis by 

 Burton, are embraced in that work under the species Pihlite, 

 and the definite establishment of Shepard's species has appa- 

 rently awaited the fuller investigation dependent upon a re- 

 discovery of a purer material in sufficient supply. 



At Chesterfield Hollow, in the mass of coarse Orthoclase- 

 granite which forms the southern abutment of the hill above 

 the village, I found a small and long-abandoned opening, and 

 re-opened and excavated it during portions of three successive 

 summers. The Spodumene was here found almost altogether 

 in the form of well-defined crystals, often thickly grouped and 

 traversing the smoky Quartz in every direction, and showing all 

 the stages of alteration into Cymatolite, from a mere envelop- 

 ing film, as an outer crust, and also dulling internally the lustre 

 of its prominent cleavage-surfaces, to a pseudomorphous altera- 

 tion of the entire crystal. Many of its crystals must have been 

 of unprecedented and enormous size, as they were found, mostly 

 in the altered condition, up to a length of 35 inches, actually 

 measured while lying in the vein, and with a diameter which 

 sometimes reached 10 or 11 inches. However they were, together 

 with their quartz-gangue, so traversed by innumerable minute 

 fissures, occupied but only feebly cemented by the films of Pyro- 

 lusite, that no perfect specimens could be extracted at all ap- 

 proaching these dimensions. On the other hand, acicular crystals 

 were observed in abundance, penetrating the Quartz in an irregu- 

 lar and confused net-work ; good single terminations were not 

 uncommon ; and even one or two short and doubly-terminated 

 crystals were found in a partially pseudomorphous condition. 

 Besides this form of alteration, several other pseudomorphs 

 after Spodumene in various materials, Killinite, Quartz, Albite, 



