ESCR - Giant's Causeway - Mineralogy

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Summary Full report
Giant's Causeway - Mineralogy	Antrim

Site number:	533
ESCC:	EC
Locality Type:	Cliff, Coastal section, Inactive scree	Status:	ASSI
Grid Reference:	C947448 Centroid
Google maps:	55.24155,-6.51118
County:	Antrim	Council area:	Causeway Coast & Glens Borough Council
Period:	Tertiary
Stages:	Eocene, Palaeocene
Lithostrat:	Antrim Lava Group

Site Description
Giant’s Causeway, Co.Antrim.
Highlights:
Tertiary basalt with zeolite minerals.
Description:
The cliffs and screes of the Causeway area are one of the best sites in Northern Ireland for finding zeolite minerals, which occur in vesicles within the upper sections of basalt lava flows. Greg and Lettsom, in their Mineralogy of Great Britain and Ireland (1858), record in the Causeway area the occurrence of natrolite, mesolite, thomsonite, stilbite, heulandite, chabazite, phillipsite, analcime, brewsterite and harmotome. The last two are barium-bearing zeolites and their occurrence at the Causeway has since been refuted. However R. Nawaz (pers. comm.) has confirmed the occurrence of a barian phillipsite, which was given the name wellsite though this name has recently been discredited (Tschernich, 1992). Recent (unpublished) analytical work by N. Moles has indicated the presence of heulandite-Ca and phillipsite-Na, both containing a few percent of strontium and barium. In addition to the list given above, Walker (1960) records the zeolite scolecite from the Causeway basalts, and also the non-zeolite minerals chlorophaeite, celadonite, opal, quartz and chalcedony. According to Walker, the screes beyond Benanouran Head demonstrate a zonal arrangement of zeolites through a single lava flow. Giant’s Causeway, Co.Antrim: road from visitor centre. Giant’s Causeway, Co.Antrim: scree below road. The only recorded occurrence in Northern Ireland of the zeolite mineral, paulingite, is in loose boulders at Portnaboe, in the central part of the scree below the road leading from the Visitor Centre to the Causeway. The source of this material is presumably in the cliffs of Weir's Snout which comprise the Causeway Tholeiite Member. The paulingite occurs as colourless, diamond-faceted crystals generally 1-2mm across. Paulingite-bearing vesicles contain no other zeolite species. Analytical studies of this material are in progress (N. Moles, 2001).
Notes:
See also Key Site 61 - Giant's Causeway.

Keywords
Minerals:	Analcime, Chabazite, Chalcedony, Natrolite, Opal, Phillipsite, Quartz, Stilbite, Thomsonite, Zeolites, Heulandite, Mesolite, Scolecite, Chlorophaeite, Celadonite, Paulingite
Rocks:	Basalt, Tholeiite
Structures:	vesicles

Access
Threats:	Inactive screes sensitive to collecting.


Record type:	ESCR report	Recorded by:	R. Nawaz and N.R. Moles
Entered by:	E M Porter
Last updated:	07 MAY 68

Enlander, I., Dempster, M. & Doughty, P., 2026. Giant's Causeway - Mineralogy, County Antrim, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=533. Accessed on 2026-11-06.

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