I ascended one, and found it was capped with trap rock in amygdaloidal nodules.
"Journal of an Expedition into the Interior of Tropical Australia In Search of a Route from Sydney to the Gulf of Carpentaria (1848) by Lt. Col. Sir Thomas Livingstone Mitchell Kt. D.C.L. (1792-1855) Surveyor-General of New South Wales"
Thomas Mitchell
Porphyrites are usually porphyritic, and frequently amygdaloidal.
"Geology"
James Geikie
Occasionally we meet with igneous rocks which are more or less vesicular and amygdaloidal throughout their entire mass.
"Geology"
James Geikie