ALBITIO GRANITE. 329 



THE CRUSHING OF MINERALS IN THE ALBITIC GRANITE. 



In the Slimmer of 1885 the pegmatite dike on Wahuit Hill, in Hunt- 

 ington, was reopened for me by Mr. Frank L. Nason. The spodumene 

 crystals obtained were large — larger than most of those obtaini'd pre%'iously. 

 They were clear-gray, Avithout the shade of flesh-color of those before 

 obtained, and were covered with dendrites, which also penetrated every- 

 where into the perfect cleavage. Several fine twins occurred, Init foi- the 

 most part they were not well terminated. The largest cr^-stal was '2n by 

 7J by 3^ inches. The crystals bear abundant evidence of tlie violent 

 pressure to which they have been subjected since their formation, several 

 large, perfectly terminated crystals a foot long being several times obliquelv 

 sheared off and the i)arts slipped one-eighth to one-fourth of an inch and 

 recemented; and the largest crystal, whose dimensions are given above, i.s 

 broken across or sharply folded into "monoclinal fle.xures" more than forty 

 times. Other large crystals are bent over as much as 45° in a great curve, 

 one sharply a full 90°, and without a crack.^ 



The feldspar (microcline) occurs in masses as large as one's head, often 

 in part green. The cleavelandite is not distinguishable from that of Chester- 

 field. Tourmaline appears in large, rude, black crystals. ( rranular masses 

 of honey-yellow manganesian garnet (intermixed with feldspar) as large as 

 an egg have by their decomposition furnished the material for the abun- 

 dant dendi'ites. These latter masses are at times punched into the great 

 spodumenes as if these had been plastic as wax. 



There is in the collection at Amherst a crystal of tourmaline from the 

 Clarke ledge, once figured by President Hitchcock," which is broken across 

 fifteen times and the parts moved into a position en Echelon and recemented 

 by quartz, and I have a crystal of beryl from Huntington similarly affected. 



HYDROTHERMAL CHANGES IN THE ALBITIC GRANITE VEINS. 



Pseudomorphs. — Julien has described a most interesting series of pseudo- 

 morphs in these dikes, produced by alkaline (mainly sodic) silicate solutions, 

 by which spodumene is changed into cymatolite, killinite, albitic granite, 

 muscovite, albite, and quartz, the lithia being replaced by the other 



' For figures of these crystals see Minerological Lexicon, uuder " Spodumene": Bull. U. S. Geol. 

 Survey No. 126, 1895, p. 159. 



-E. Hitchcock, Geol. Mass., p. 702. 



