Having the base in excess. Mineralogy. (An igneous rock) Having little silica in proportion to the amount of lime, potash, magnesia, etc. present.

Geology. Of igneous rock: relatively rich in silica; (of volcanism) involving silica-rich magma. Contrasted with basic, adj. 2b. Cf. acidic, adj. 1b.

Of an igneous rock: having a silica content that is lower than that of the basic rocks (cf. basic, adj. 2b), spec. less than 45 per cent by…

Designating a primary category of igneous rocks whose chemical composition can be expressed in terms of a group of standard minerals which are…

Also Sal. = sial, n. (now superseded by that term). Obsolete.

Of an igneous rock: composed chiefly of mafic minerals. Also as n.

of the nature of, containing, or resembling komatiite.