230 



ironhydroxide has penetrated between the aggregates of rauscovite. 

 Though the rock does Jiot contain andaliisite, it is yet likely, that 

 it belongs to the contactmetamorphic formations. 



Spotted clay slates such as Verbeek discovered ^) in the isle of 

 Labobo (Banggai Isles) were not found among the rocks ofTaliabu. 



A group of rocks that have likewise been transformed by contact 

 with granite, but belong to the Jurassic system, are of a quite different 

 nature. Van Nouhuys indicated already on his map a hornfelsmass 

 in the region of the source of the Wai Najo, whilst for the rest he 

 detected normal Jurassic sediments partly covered with alluvial 

 sediments from the source of the river to its upper course. As 

 appears from a subsequent investigation these hornfelslike masses 

 belong to the calcsilicate-i-ocks. ') Van Nouhuys collected specimens 

 of these in the Wai Najo and its right tributary, the Baja, and 

 likewise in the Wai Tabana and the Langsa. Tliey are all dense, 

 very hard splintery and usually of a greenish-grey colour which, 

 in some spots, changes into whitish and occasionally into dark 

 grey. Some of those rocks as those of the Langsa consist of parallel 

 strata sharply separated from one another, perceptible to the naked 

 eye, and of a whitish- and blackish-grey colour. 



The epidote is a mineral, which, according to the microscopic 

 examination, is never wanting, it is almost always represented by 

 the optically-positi\e klinozoisite. which is usually colourless but 

 occasionally provided with a light-yellow tint. The always irregularly 

 shaped grains can easily be recognized by theii- strongly refractory 

 power and theii' other optical properties. Some parts of the lime- 

 siUcatehonifch originating from the Wai Najo consist chiefly of 

 aggregates of this mineral, among which is found a colourless 

 groundmass that cannot be nearer defined and often contains infini- 

 tesimal parts of dust. In other |)arts this groundmass forms the chief 

 constituent of the rock, in which klinozoisite occurs then only in 

 the form of isolated grains. 



Besides the many and very little grains of klinozoisite in the 

 lime-silicate hornfels found in the river Langsa, prisms of tourmaline 

 and needles of rutile(?) were occasionally met with. According to 

 the microscopic examination the difference between the light and 

 the dark strata is only caused by the fact that the latter are rich 

 in infinitesimal parts of dust. 



^) Molukken Verslag, p. 219. 



^) Bijfliage tot de kennis van het eiland Taliaboe, p. 11^0, 1193, 1194, 

 map N". XX. 



