Scawt Hill is a volcanic plug in County Antrim, Northern Ireland, in the borough of Larne, 5 km from the village of

Ballygally Ballygally or Ballygalley (, IPA: �bˠalʲəˈɟɛhlʲiː is a village and holiday resort in County Antrim, Northern Ireland which lies on the Antrim coast, approximately north of Larne. It is also a townland of and is situated in the c ...

.Habitas, Scawt Hill, Site Description
/ref> It gets its name from the

Ulster Scots Ulster Scots, may refer to: * Ulster Scots people * Ulster Scots dialect Ulster Scots or Ulster-Scots (', ga, Albainis Uladh), also known as Ulster Scotch and Ullans, is the dialect of Scots language, Scots spoken in parts of Ulster in North ...

"" meaning scaly, scabby or rugged.Mountain Views, Walk Sallagh Braes to Glenarm
/ref> Alternatively, '' 'scawt' '' meaning scruffy and contemptible, and when applied to rocks, covered in barnacles.Dictionary of the Scots Language
/ref>

Discovery of minerals

Scawt Hill is notable for being the

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

for several hydrated

calcium silicate Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO·SiO2. It is also referred to by the shortened trade name Cal-Sil or Calsil. It occurs naturally as the mineral larnite. ...

s,Mineral and Locality Database, Scawt Hill
/ref> that is, the place where they were first identified. These minerals were formed when the existing chalk of the area was intensely altered by the intrusion of the feeder tube of an ancient volcano, now long since cooled and eroded to its roots.Wilson, H E et al (1986) Geological Survey of Northern Ireland, HMSO Minerals that were first discovered at Scawt Hill: * Larnite (''calcium orthosilicate'') a natural form of belite discovered in 1929Mineral and Locality Database, Larnite
/ref> and named after Larne, the nearest town *

Scawtite Scawtite is a hydrous calcium silicate mineral with carbonate, formula: Ca7(Si3O9)2CO3·2H2O. It crystallizes in the monoclinic crystal system as thin plates or flat prisms. Scawtite was first described in 1929 for an occurrence at Scawt Hill in N ...

in 1929 * Portlandite in 1933Web Mineral, General Portlandite Information
/ref> * Hydrocalumite in 1934 * Rankinite in 1942 * Bredigite in 1948 In all, 28 minerals have been found at this site.Habitas, Scawt Hill, Summary
/ref>

Volcanic plugs in Northern Ireland

Over 30 volcanic plugs are dotted through Northern Ireland, mostly along the Antrim coast like Scawt Hill, although they are relatively rare throughout the rest of Ireland. Volcanic plugs are often easy to spot. Their harder rock erodes away more slowly than their surroundings so they rise above the landscape as a hill. The largest volcanic plug in Northern Ireland is the oval-shaped Slemish. At its widest, Slemish is over 1 km in diameter. Scawt Hill is more of a typically sized example. This olivine dolerite plug is 270 m x 180 m wide and rises 30 – 60 m above the Cretaceous white limestone (chalk), although the Antrim plateau around it is typically basalt. Scawt Hill - geograph

Due to the volcanic intrusion the chalk around Scawt Hill has been transformed by high temperature and low pressure

thermal metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of c ...

, developing the large and unusual range of calc-siliate minerals that have attracted interest. The rocks inside the vent were also changed by the contact, producing a sequence of alkali mafic igneous rocks as the magma assimilated the chalk, reducing the silica in the magma and leading to larger

grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refer ...

near the contact.

Early description of Scawt Hill

Cecil Edgar Tilley, writing for the Mineralogical Magazine in 1929, was the first to appreciate the potential of the dolerite-limestone contact at Scawt Hill. Tilley named scawtite and larnite, and later, rankinite, and his writings inspired many others to find similar relationships between rocks worldwide.

Protected status

In 1995, Scawt Hill was categorised as an Area of Special Scientific Interest, not just for its international importance to geology, but for its plant life, where chalky and

alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...

conditions are in close proximity, and for its conditions for breeding birds.Scawt Hill, ASSI, Protected Areas, Department of the Environment NI
/ref>

Ulster Way

Scawt Hill is on the Ulster Way, part of a series of walking routes which encircle Ulster. It is passed by between the Black Hill and the Sallagh Braes.Walk NI, The Ulster Way
/ref>

RAF plane crash

17 September 1943 a Royal Air Force, Vickers Wellington (W5647) had departed from RAF Limavady on a training flight over the Irish Sea. The weather at RAF Limavady was getting worse and the crew was ordered to return to base. While flying low the aircraft crashed into the side of Scawt Hill, killing one of the six crew.

References

{{Geology of Northern Ireland Mountains and hills of County Antrim Volcanic plugs of Northern Ireland Paleogene volcanism Paleogene Ireland Protected areas of County Antrim Aviation accidents and incidents locations in Northern Ireland