Long Gilbert

Long Gilbert QuarryThe Long Gilbert Quarry sits above the White Rocks at the eastern end of the East (or Curran) Strand. It is a limestone quarry from which stone was taken for many hundreds of years but which has not been worked for at least 75 years. Some of the infrastructure is still evident including the two lime kilns where limestone (Calcium Carbonate) would have been burned to produce quicklime (Calcium Oxide) which has been used since the earliest times in building mortars and Roman concrete, as a stabiliser in mud renders and floors and a soil conditioner in agriculture. The addition of water to quicklime produces slaked lime (Calcium Hydroxide) which has a significant application as a flocculant, in water and sewage treatment forming a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product.Mechanism for Producing Limelight

Quicklime is also used today in steelmaking, the manufacture of cement and aerated concrete blocks, glass making, petroleum distillation and paper making. In the 19th century before the invention of electric lighting theatrical productions used a form of spotlight known as a Limelight. This utilised the fact that when a cylinder of quicklime is heated to 2,400°C by an oxyhydrogen flame it emits an intense glow which could be controlled by an operator and focused unto the stage using a system of glass lenses. The term Limelight is still used today and refers to someone in the public eye who is said to be “in the limelight“.

The name of the quarry is said to come from a tall, gangly native of North Antrim who was Jester to Lord Antrim at Ballymagarry many hundreds of years ago. Believed to be called Gilbert MacLaughlin but known as Long Gilbert due to his height and long legs he was said to run with the hounds during fox or deer hunts. Legend claims that he was swifter than the hounds and could run all day without tiring. On one occasion it is said that the hunted animal lead the pack of hounds and Long Gilbert towards the cliff edge above the White Rocks at great speed; and being unable to stop all plunged over the edge to their deaths. The place where they fell is now the site of Long Gilbert Quarry.

These cliffs of Cretaceous rocks formed some 75 million years ago when Portrush (and most of Ireland) formed the bed of a warm shallow lake covered in a white, chalky ooze composed of the minute plates of a group of planktonic marine algae called coccoliths. These oozes lithified into the rocks now named the Ulster White Limestone Formation. Within this formation are 14 identifiable Chalk Members of which 6 appear at the White Rocks and three, of particular importance are exposed in Long Gilbert Quarry – Portrush Chalk, Ballymargarry Chalk and Tanderagee Chalk. Source: Earth Science Conservation Review

The lowest, the Portrush Chalk Member, over 14m thick, is exposed on the eastern quarry face and is easy to recognise because it is sandwiched between two units containing massive flints. It has been subdivided into four beds determined by their characteristic flint bands and the presence or absence of certain fossils. The Portrush Chalk has many wavy bedding planes suggesting considerable disturbance of the sea at that time: bedding planes are smoother for the later members.

The second, the Ballymagarry Chalk Member, is 11m thick and divided into 3 beds, the first with 9 levels of nodular flints, the second, unmistakeable because it contains the largest flint nodules anywhere in Northern Ireland as well as a few paramoudras (enigmatic, large cylindrical to flask-shaped, hollow flints standing erect in the beds). The third bed lies immediately beneath the prominent Long Gilbert Flint Band. The member is best viewed on the south face of the central quarry.

The third, the Tanderagee Chalk Member, has 5 divisions and is about 14 m thick. Again a combination of diagnostic flint bands and fossils is employed in the recognition of the divisions with long belemnites featuring for the first time.

All geological formation names are based on particular exposed sections of rock, ideally showing the full thickness of the section, its main features but particularly defining its base; such sections are described as type sections or stratotypes. The importance of the stratotypes gives the sequence from Sliddery Cove up through Long Gilbert Quarry national significance.

Source: Earth Science Conservation Review