Igneous dikes are planar to irregularly-planar igneous intrusions that cut across country rocks. They can be thin or extremely thick & they can be vertical or obliquely-oriented.
These photos linked to below show dikes of various lithologies (granite, pegmatite, aplite, andesite, basalt/diabase, lamprophyre, clinopyroxene-garnet-oligoclase granulite, minette, rhyolite) intruding country rocks of various lithologies.
The photos linked to below were taken in Colorado (Glenwood Canyon; Black Canyon of the Gunnison area; Cripple Creek Gold District), Wyoming (Absaroka Range), Montana (Butte), California (Sierra Nevada Mountains), New York State (Adirondack Mountains), Maine (Acadia National Park), New Hampshire (Ruggles Mine), New Mexico (Ship Rock area), and South Dakota (Black Hills).
Igneous dikes photos