WARREX A\D PALACHE. — QUIN'CY PEGMATITES. 145 



contains 14.")1 per cent of Fe2()8 and 21.43 per cent of FeO. Or the 

 aegirite contains 22.98 per cent of iron, the riebeckite, 26.S1 per cent, a 

 difference of 3.<s8 per cent. There is an even greater diff"erence in the 

 soda content, not to mention minor dilVerences. To convert one into 

 the other calls upon the mineraHzers and pressure, besides oxidizing or 

 reducing a considerable amount of iron, to actually aff'ect a consider- 

 able change in the chemical composition. It seems more reasonable to 

 assume that the development of one or the other of these minerals 

 depends primarily upon the relative concentrations at a given point of 

 the various constituents which go to form the minerals. 



The separation, whether by actual crystallization or by some process 

 of molecular segregation prior to actual crystallization, of the feldspar 

 and a part at least of the riebeckite from the magma, had the effect of 

 greiitly increasing the concentration of the more volatile or li(iuid con- 

 stitutents, such as water, tiuorine, also silica, the aegirite radical, zircon, 

 etc., in the residual portions of the magma. The habit which the 

 minerals crystallizing from such portions of the magma might or may 

 have assumed, also the habit of the main part of the feldspar and 

 riebeckite, has been somewhat modified by movements in the rock, 

 either during the later stages of crystallization or subsequently, or 

 both. This is indicated by the straining and granulation of the quartz ; 

 the deorientation of the portions of the feldspar, particularly the mar- 

 ginal portions ; the development (recrystallization) of the smaller albite 

 crystals about and between the larger grains ; the frayed, granular, 

 broken or otherwise irregular character of the last formed riebeckite 

 and aegirite. Evidence of strong movements, accompanied by solvent 

 and crystallizing action, are to be seen in the presence of the frag- 

 ments in the large central pocket of the Fallon pipe, in the solution 

 and recrystallization recorded there, and in the many seams, now 

 sealed with relatively coarse riebeckite, feldspar, etc., which cross the 

 granite in many places ; also in the small quartz veins cutting the 

 granite in some of the quarries. There is also abundant outside evi- 

 dence that the granite has passed through profound periods of dynamic 

 disturbance since intrusion. It was during some period or periods of 

 movement^ accompanied perhaps by an increase of temperature and 

 possibly by a recurrence of pneumatolitic activity, that the development 

 of the greater number of the minute cavities and the crystallizations of 

 aegirite and riebeckite in the feldspar is thought to have taken place. 

 Their location is generally in positions most favorable to the jjonetra- 

 tion of solutions, viz. — along the boundaries of twinning or i)erthite 

 lamellae, or along cleavage directions. Other crystalliziitions of like 

 origin but varying habit lie about the borders of the aegirite-ricbeckite 



