Igneous [adjective]

The most ancient and lowest stratum of this igneous formation is a compact conglomerate known as tufa lithoide.

The "erratics" comprised a great variety of metamorphic and igneous rocks, and, on a more limited scale, sedimentary types.

The beacons were found to be part of a horizontal, stratified series of sandstones underlying the igneous rock.

The metamorphism of the igneous rocks is regional in nature and has the same increase from west to east as the sediments.

The stone formation bears the usual indications of aqueous and igneous deposits, but more of the former than the latter.

Felspar is one of the principal constituents of almost all igneous rocks, such as granite, diorite, and basalt.

The Igneous rocks are those which owe their origin to the action of the internal forces of the earth's crust.

The zeolites occur very commonly in cavities in igneous rocks, and also in mineral veins.

Certain igneous rocks frequently shew division planes which meet each other in such a way as to form a series of polygonal prisms.

But as a rule they are less hard than crystalline igneous rocks, and in many cases are loose and crumbling.