Sunimarv of Geological Observations. 



everywhere rich in tourimdinc and metallic ores, ihitenift; rlinmiife, hemafife and 

 iiKKjnefifc. In some places (jarnet and apatite are also noticed, while in the 

 schistose surfaces fine fibrous aggregates of cijanite and silliinanite are common. 



On the Kichuchu Plain, Ijesides the existence of a labradorite gneiss, the 

 presence is conspicuous of some dikes of basalt, which ramify and intersect 

 the gneiss-mica-schist formation. This basalt, which constitutes the only 

 evidence of recent volcanic action met by us in the range, is microcrystalline 

 and of holocrystalline type. On the Biamba Plain I further met a diabase in 

 which the opaque element is represented by chroiiiite alone. 



Towards 12,000 feet the zone of the mica-schists disappears, and the 

 greenstones come to the surface ; these constitute exclusively Mts. Baker and 

 Stanley, and are associated with gneiss on the other heights visited by the 

 expedition. On the western slope of Mt. Baker the identical mica-schists 

 reappear, which we had met in the Mobuku Valley, but on the west side they 

 range somewhat higher than on the east. 



The zone of the greenstones is constituted essentially of an arnphiholite 

 schist, in which the schistose element is more or less evident ; it is usually micro- 

 crystalline and formed of hornhlende with quartz, and in the second place felspar 

 (mostly andesite), and in this case it passes over to a diorite schist. From this 

 amphibolic schist are developed some varieties due to the substitution of 

 actinolite for hornblende, or else to its association with garnet, biotite and pyroxene. 



Abundant in these rocks are ihnenite and ejndoie, the latter also forming 

 numerous beds, veins and nodules, some of which are of extraordinary thickness, 

 as much as 30 feet in the longer axis. Moreover, numerous beds of quartzite 

 everywhere accompany the amphibolic schists, with which in the various 

 mountains are associated other rocks in the following way : — 



Mt. Baker. — (Juartziferous diorite ; compact amphibolite which forms the 

 Edward Peak, on the summit of which are numerous fulgurites ; cri/sfalline 

 limestone ; chlorite schist, epidosyte, grenatite ; diabase. 



At several points on this mountain are noticed some lenticels, geodes and 

 small veins of pyrites, calco-pyrites and ilmenife, with felspars, quartz and calcite ; 

 on Wollaston Peak a small vein of galena with a gangue of calcite crops out. 



Mt. Stanley. — Compact amphibolite ; amphibolic schist with large garnets, 

 diorite and labradorite dimite which forms the Alexandra Peak, and probably 

 also the Margherita ; it is noted for its various types of fnlgii rites, epidosites and 

 diabase. 



On this mountain also pyrite and especially ilmenite are plentiful, as are 

 also copper ores : chalco-pyrite tetrahedrites, malachite. 



Mt. Luigi di Savoia. — -Here also amphiliolic schist crops out, although 



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