Basalt. One of the most common varieties of the Trap-rocks. It is a dark green or black stone, composed of augite and felspar, very compact in texture, and of considerable hardness, often found in regular pillars of three or more sides called basaltic columns. Remarkable examples of this kind are seen at the Giant's Causeway, in Ireland, and at Fingal's Cave, in Staffa, one of the Hebrides. The term is used by Pliny, and is said to come from basal, an Æthiopian word signifying iron. The rock often contains much iron.
Basin" of Paris, "Basin" of London. Deposits lying in a hollow or trough, formed of older rocks; sometimes used in geology almost synonymously with "formations," to express the deposits lying in a certain cavity or depression in older rocks.
Belemnite. An extinct genus of the order of molluscous animals called Cephalopoda, having a long, straight, and chambered conical shell. Etym., βελεμνον, belemnon, a dart.
Bitumen. Mineral pitch, of which the tar-like substance which is often seen to ooze out of the Newcastle coal when on the fire, and which makes it cake, is a good example. Etym., bitumen, pitch.
Bituminous Shale. An argillaceous shale, much impregnated with bitumen, which is very common in the Coal Measures.
Blende. A metallic ore, a compound of the metal zinc with sulphur. It is often found in brown shining crystals; hence its name among the German miners, from the word blenden, to dazzle.
Bluffs. High banks presenting a precipitous front to the sea or a river. A term used in the United States of North America.
Botryoidal. Resembling a bunch of Grapes. Etym., βοτρυς, botrys, a bunch of grapes, and ειδος, eidos, form.
Boulders. A provincial term for large rounded blocks of stone lying on the surface of the ground, or sometimes imbedded in loose soil, different in composition from the rocks in their vicinity, and which have been therefore transported from a distance.