The whole formation is Archean and Primary (with a few modern plutonic outbursts), and chiefly consists of granite, felspar, quartz, gneiss, schists, amphibolite and other Archean rocks, with Primary sandstones and limestones in the basin of Lake Nyasa (a great rift depression), the river Shiré, and the regions within the northern watershed of the Zambezi river. Sandstones of Karroo age occur in the basin of the Luangwa (N.E. Rhodesia). There are evidences of recent volcanic activity on the summit of the small Mlanje plateau (S.E. corner of the protectorate: here there are two extinct craters with a basaltic outflow), and at the north end of Lake Nyasa and the eastern edge of the Tanganyika plateau. Here there are many craters and much basalt, or even lava; also hot springs.
Gold has been found in the Shiré Highlands, in the hills along the Nyasa-Zambezi waterparting, and in the mountainous region west of Lake Nyasa; silver (galena, silver-lead) in the hills of the Nyasa-Zambezi waterparting; lead in the same district; graphite in the western basin of Lake Nyasa; copper (pyrites and pure ore) in the west Nyasa region and in the hills of North Western and North Eastern Rhodesia; iron ore almost universally; mica almost universally; coal occurs in the north and west Nyasa districts (especially in the Karroo sandstones of the Rukuru valley), and perhaps along the Zambezi-Nyasa waterparting; limestone in the Shiré basin; malachite in south-west Angoniland and North Western Rhodesia; and perhaps petroleum in places along the Nyasa-Zambezi waterparting. (See also Rhodesia.)
No part of the country comes within the forest region of West Africa. The whole of it may be said to lie within the savannah or park-like division of the continent. As a general rule, the landscape is of a pleasing and attractive character, well covered with vegetation and fairly well watered. Actual forests of lofty trees, forests of a West African type, are few in number, and are chiefly limited to portions of the Nyika, Angoniland and Shiré Highlands plateaus, and to a few nooks in valleys near the south end of Tanganyika. Patches of forest of tropical luxuriance may still be seen on the slopes of Mounts Mlanje and Chiradzulu. On the upper plateaus of Mount Mlanje there are forests of a remarkable conifer (Widdringtonia whytei), a relation of the cypress, which in appearance resembles much more the cedar, and is therefore wrongly styled the "Mlanje cedar." This tree is remarkable as being the most northern form of a group of yew-like conifers confined otherwise to South Africa (Cape Colony). Immense areas in the lower-lying plains are covered by long, coarse grass, sometimes reaching 10 ft. in height.
Most of the West African forest trees are represented in British Central Africa. A full list of the known flora has been compiled by Sir W. Thiselton-Dyer and his assistants at Kew, and is given in the first and second editions of Sir H. H. Johnston's work on British Central Africa. Amongst the principal vegetable products of the country interesting for commercial purposes may be mentioned tobacco (partly native varieties and partly introduced); coffee (wild coffee is said to grow in some of the mountainous districts, but the actual coffee cultivated by the European settlers has been introduced from abroad); rubber - derived chiefly from the various species of Landolphia, Ficus, Clitandra, Carpodinus and Conopharygia, and from other apocynaceous plants; the Strophanthus pod (furnishing a valuable drug); ground-nuts (Arachis and Voandzeia); the cotton plant; all African cultivated cereals (Sorghum, Pennisetum, maize, rice, wheat - cultivated chiefly by Europeans - and Eleusine); and six species of palms - the oil palm on the north-west (near Lake Nyasa, at the south end of Tanganyika and on the Luapula), the Borassus and Hyphaene, Phoenix (or wild date), Raphia and the coco-nut palm.
The last named was introduced by Arabs and Europeans, and is found on Lake Nyasa and on the lower Shiré. Most of the European vegetables have been introduced, and thrive exceedingly well, especially the potato. The mango has also been introduced from India, and has taken to the Shiré Highlands as to a second home. Oranges, lemons and limes have been planted by Europeans and Arabs in a few districts. European fruit trees do not ordinarily flourish, though apples are grown to some extent at Blantyre. The vine hitherto has proved a failure. Pineapples give the best result among cultivated fruit, and strawberries do well in the higher districts. In the mountains the native wild brambles give blackberries of large size and excellent flavour. The vegetable product through which this protectorate first attracted trade was coffee, the export of which, however, has passed through very disheartening fluctuations. In 1905-1906, 773,919 lb of coffee (value £16,123) were exported; but during this twelve months the crop of cotton - quite a newly developed product, rose to 776,621 lb, from 285,185 lb in 1904-1905. An equally marked increase in tobacco and ground-nuts (Arachis) has taken place.
Beeswax is a rising export.