The platy minerals have also a perfect cleavage parallel to their flat surfaces, while the fibrous species often have two or more cleavages following their long axes; hence a schistose rock may split not only by separation of the mineral plates from one another but also by cleavage of the parallel minerals through their substance.
Specular haematite forms a constituent of certain schistose rocks, such as the Brazilian itabirite.
In Ankole and Koki rocks consisting of granular quartzite, schistose sandstone, red and brown sandstone, and shales with cleaved killas rest on the Archean platform and possibly represent the Lower Witwatersrand beds of the Transvaal.
Most of tie Archean rocks fall into one or the other of two great series, a schistose series and a granitoid series, the latter being in large part intrusive in the former.
Other minerals, which are not found in commercial quantities, are lead in the form of galena, in Sussex county; graphite, in the crystalline schistose rocks of the Highlands; molybdenum, in the form of a sulphide, in Sussex county; and barytes in Mercer and Sussex counties.
Nearly all known sorts of schist are represented in the schistose nart of the system.
Geological research shows that the land surrounding the lake consists of gneiss, quartz and schistose rocks, covered, in the higher regions, with marl and red clay, and in the valleys with a rich black loam.
West of the volcanic region, nearer to Lake Victoria and the Eastern province, ironstone, granite, gneiss and schistose formations predominate, with phonolite in places.
Metamorphosed sedimentary rocks are widely distributed in the schistose series, but they are distinctly subordinate to the meta-ignecius rocks, and they are so highly metamorphic that stratigraphic methods are not usually applicable to them.
It occurs crystallized, commonly in cubes, in schistose and slaty rocks, and less abundantly in the younger sedimentary deposits.