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Both these rocks are composed of triclinic feldspar and augite with more or less olivine, magnetic or titaniferous oxide of iron, and usually a little nepheline, leucite, and apatite; basalt usually contains considerably more olivine than melaphyre, but chemically they are closely allied, although the melaphyres usually contain more silica and alumina, with less oxides of iron, lime, and magnesia, than the basalts.

Tridymite: 100.0 2.3. Orthoclase. Orthoclase. Albite. Oligoclase. Oligoclase. Labradorite. Labradorite. Anorthite. Anorthite. Leucite. Nepheline. Nepheline. Muscovite. Lepidolite. Li 4.85. Biotite. Biotite. Phlogopite. Margarite. Chlorite. Rapidolite. Talc. 63.00 .... .... trace .... 33.60 .... .... W 3.10 2.78. Tremolite. St. Actinolite. Hornblende. Uralite. Augite. Augite. Diallage.

Recent eruptive rocks, mainly basalts, form a line of hills almost bare of vegetation between Benguella and Mossamedes. Nepheline basalts and liparites occur at Dombe Grande. The presence of gum copal in considerable quantities in the superficial rocks is characteristic of certain regions. Climate. With the exception of the district of Mossamedes, the coast plains are unsuited to Europeans.

Miascite is one of the varieties of syenite most frequently spoken of; it is composed chiefly of orthoclase and nepheline, with hornblende and quartz as occasional accessory minerals. It derives its name from Miask, in the Ural Mountains, where it was first discovered by Gustavus Rose. ZIRCON-SYENITE is another variety closely allied to Miascite, but containing crystals of Zircon.