Summary of Geological Observations. 
everywhere rich in tourmaline and metallic ores, ilmenite, chromite, hematite and 
magnetite. In some places garnet and apatite are also noticed, while in the 
schistose surfaces fine fibrous aggregates of cyanite and sillimanite are common. 
On the Kichuchu Plain, besides 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 chromite 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 amphibolite 
schist, in which the schistose element is more or less evident; it is usually micro¬ 
crystalline and formed of Im'nblende 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 ilmenite and epulote, 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 .—Quartziferous diorite; compact amphibolite which forms the 
Edward Peak, on the summit of which are numerous fulgurites; crystalline 
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 ilmenite, 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 diorite which forms the Alexandra Peak, and probably 
also the Margherita; it is noted for its various types of fulgurites, epidosites and 
diabase. 
On this mountain also pyrite and especially ilmenite are plentiful, as are 
also copper ores : chalco-pyrite tetraliedrites, malachite. 
Mt. Luigi di Savoia.—H ere also amphibolic schist crops out, although 
389 
