When single crystals of any mineral are scattered through a rock, so as to be readily distinguished from the compact or crystalline base, the rock becomes porphyritic.
"Geology"
James Geikie
What is meant by the terms amygdaloidal and porphyritic?
"Geology"
James Geikie
To the right or W. side are the valleys of Lacour and Enfer, separated from each other by a dyke of dark porphyritic trachyte.
"The South of France--East Half"
Charles Bertram Black