See the photo below to help understand these terms.
A dike is:
“A discordant tabular body of igneous rock that was injected into a fissure when molten, that cuts across the structure of the adjacent country rocks, and which usually has a high angle of dip. It should not be confused with a vein.” United States Bureau of Mines
“Said of a feature having two dimensions that are much larger or longer than the third, sub as an igneous dike, or a geomorphic feature such as a plateau.” Bates and Jackson, A Dictionary of Geological Terms
“A dike is a tabular body of igneous rock cutting across bedding and hence, discordant.”
Contrast with a vein:
“In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation.”
To me, what the authors suggest is that a dike is merely rock whereas a vein contain minerals. Can anyone help me here?
Photo: On Interstate 11 near Hoover Dam