PHALEn] new occurrence OF UNAKITE 315 



kite — as it proves when examined macroscopically. Though feld- 

 spar is not readily apparent to the naked eye, it may be seen in thin 

 sections largely replaced by epidote. A small amount of untwinned 

 plagioclase is also present. The remaining minerals are zircon, 

 hydrous and anhydrous iron ore, and apatite. The derivation of this 

 rather rare rock from the unakite is very apparent ; it represents an 

 advanced stage of epidotization. 



Olivine-basalt 



The mass of the rock constituting the ridge in this vicinity, and to 

 whose resistance the ridge owes its superior height, is a dull green 

 aphanatic mass whose constituents, excepting an occasional speck of 

 epidote and partially altered olivine, cannot be determined with the 

 naked eye. This olivine-basalt is younger than the granite lying to 

 the east, and may be later than the boss of akerite, though future 

 work only will settle this point definitely. Its intrusion in the 

 granite has resulted in profound metamorphism of the latter rock in 

 the border zones, the ordinarily massive rock having become decid- 

 edly gneissoid. Large fragments of basalt, generally epidotized, 

 occur near the contact, which appear as though they had solidified, 

 had been wrenched from the wall, and had then fallen back into the 

 magma in its upward motion. Columnar joining in the basalt is well 

 developed north of the Gap at Franklin Cliff. 



The olivine of the basalt occurs as phenocrysts, sometimes 3 or 

 4 mm. in diameter, and generally presents a thoroughly corroded 

 periphery, surrounding a tolerably fresh nucleus. At times even 

 this has disappeared, leaving a brownish red mass to mark its former 

 position. The results of the microscopic examination indicate almost 

 complete alteration, and the determinable constituents are few in 

 number, consisting chiefly of feldspar, pyroxene, olivine, magnetite, 

 with chlorite, epidote, and iron ore. The feldspar and pyroxene con- 

 stitute the mass of the rock. Imbedded here and there in the mass 

 occurs the olivine, partially filled with a network of brown decompo- 

 sition products, mostly iron oxide. Besides this ocherous mate- 

 rial, there are amorphous, cloud-like masses scattered about in abun- 

 dance, generally associated with the ferruginous constituents and 

 evidently produced as a result of their decomposition. There are 

 present in addition, epidote and chlorite, the latter in scales or shreds 

 polarizing with dull-gray or bluish tints. In some green phases, 

 epidote constitutes the bulk of the rock. 



