They are nearly all of porphyritic diabase.
"Rough Stone Monuments and Their Builders" by T. Eric Peet
Surface eruption of diabase.
"History and Comprehensive Description of Loudoun County, Virginia" by James W. Head
Such intrusive rocks are porphyries, diabases, etc.
"The Economic Aspect of Geology" by C. K. Leith
In Devonshire diabases and tuffs are found in the middle division.
"Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 3" by Various
Diabases and peridotites had been formed during the Lower Cretaceous in the San Luis Obispo region.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 6" by Various
Quartz porphyry, diabase and diorite appear in the Ardennes.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1" by Various
Dykes of diabase and diorite are abundant.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7" by Various
The upper part of the Maluti range consists of flows of melaphyres and diabases belonging to the volcanic beds.
"Encyclopaedia Britannica, 11th Edition, Volume 3, Slice 4" by Various
In some of the folds of Arenig cherts diabase lavas appear, which occupy small lenticular areas.
"Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 10" by Various
Serpentines, peridotites and diabases are interstratified with the Eocene deposits.
"Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 2" by Various
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