﻿Vol. 6 1.] ON KOCKS FKOM THE CONGO FEEE STATE. 659 



No. 34, Mount Combe. — This rock is almost identical with 

 Nos. 35 & 36. 



No. 21, from a point south of Mount Gaima. — This is part of 

 the same gneissie mass as Nos. 34, 35, & 36. The amount of 

 sphene is considerable. 



No. 35 a, Mount Combe (diabase). — A dark greenish-grey com- 

 pact rock, of medium grain. 



The section shows much pale-brown augite in ophitic relation- 

 ship with the felspar. The felspar is moderately fresh, but is 

 spotted with dusky alteration-products. The crystals are stout, 

 lath-shaped ; Carlsbad and albite- twinning are both common, most 

 of it is near labradorite. A little fresh felspar and some quartz 

 occur with occasional micrographic structure between the 

 larger felspars. Iron-ores are in irregular grains and skeletons. 



No. 44, Arebi. — A dark -green, coarse-grained rock, with 

 hornblende greatly predominating; dull felspar and quartz occupy 

 the spaces between the crystals. The green hornblende is in 

 large plates and idiomorphic crystals ; the plates enclose flakes of 

 biotite, the idiomorphic hornblende, and some olivine in a poeci- 

 litic manner. All the felspars are greatly altered, micacized. 

 Quartz appears in patches of fair size, enclosing the felspar 

 and a few needles of actinolite. Some granular epidote 

 occurs in the altered felspars. A colourless amphibole is present 

 in small irregular patches. 



The rock might be regarded as a hornblende-gabbro, and in 

 appearance it is not unlike an olivine-poor hornblende-picrite. 



No. 44 a, from the Arebi District, several miles north of No. 44 

 (sheared diabase). — A pale-greenish rock, evidently much crushed 

 and slightly foliated, with shiny surfaces along the direction of 

 foliation. 



The thin slice shows a highly-altered rock, apparently a sheared 

 diabase. The shearing is not very evident in the section, and 

 many of the felspars retain their form. A very fine epidote-dust 

 is prevalent ; calcite, talc, and chlorite are also present. 



No. 17, near Vankerckhovenville (gneiss). — A fine-grained 

 greenish-grey rock, consisting chiefly of well-foliated granular 

 felspar and quartz. 



No. 37, near the confluence of the Motu Elver with the Arebi. — 

 A dull-green rock, compact and slaty in appearance, slightly shiny 

 on fresh surfaces ; weathering brown. The thin section shows 

 a fine-grained feltwork of chlorite with granular quartz ; the 

 whole is liberally sprinkled with small crystals of pyrites and 

 some magnetite. 



A phyllite or fine-grained chlorite-schist. 



