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McIlroy's Port to Portmuck, Island MageeAntrim
McIlroy’s Port to Portmuck, Islandmagee, Co.Antrim, June 1997.
Summary Full report
Site Type: Coastal section
Site Status: ASSI
District: Larne Borough Council
Grid Reference: D34544027
Rock Age: Tertiary
Rock Name: Antrim Lava Group
Rock Type: Amydaloidal Basalt, Pegmatite, Picrite
Minerals: Natrolite, Sodalite, Titanaugite
Other interest: dyke, volcanic vent, No Data

Summary of site:

There is a lava flow at this locality containing a high proportion of the mineral olivine. Such lavas are described a picrites and, unusually in this one, there is a 30 cm thick zone containing coarsely crystalline patches and veins. These patches and veins are pegmatites, usually created in the final stages of igneous activity when high levels of volatiles create cavities and circumstances in which large crystals, exceeding 2.5 cm long, can grow. This pegmatite is noted for the occurrence of a rare mineral, sodalite, a chlorinated sodium aluminium silicate belonging to a group called feldspathoids, similar in structure to feldspars but containing less silica.

For a description of the context of these minerals, see the general account for McIlroy's Port, record 640.

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