The Black Bell of St. Patrick, made from iron and now in the possession of the National Museum in Dublin, was a highly venerated relic on Croagh Patrick for many years.
The "Clog Dubh" is mentioned by De Latocnaye in his Frenchman's Walk through Ireland (1797 ). 'On the summit there is a little chapel at which Mass is celebrated on the Fete day and in it is a black bell for which the inhabitants have a peculiar veneration. It is used as a thing to swear on in legal matters, and no one will dare to perjure himself on it. They have strange ideas on the subject of this bell, and believe that the devil will carry them off immediately if they dare to affirm on it anything that is not true.' O'Donovan writing from Ballinrobe in 1838 states: 'at Lavally in this parish lives Hugh Geraghty, the present mayor (steward) of the relic called "Clog dubh."
According to the traditional story, as narrated by Hugh, the bell was originally of white metal, but from constant pelting at the demons who came to molest the saint on the reek, it became quite black.' This traditional story linked the bell directly to St. Patrick.
The bell was later acquired for the Royal Irish Academy by Sir William Wilde (circa 1840) who in his book Lough Corrib (1867) states: 'It had long been in the possession of the Geraghty family, near Ballinrobe, who brought it every year to the pattern held on the top of Croagh Patrick on Garland Sunday and where in the little oratory there the pious pilgrims were allowed to kiss it for a penny; and, if he had been affected by rheumatism pains, he might put it three times around his body for two pence.' The money Hugh Geraghty received from Sir William Wilde was used to pay his passage to America. Colm O'Lochlainn states in 1961 that 'the correct custom was to pass the bell three times around the body right hand wise (deiseal) in honour of the Father, Son and Holy Ghost.'
An extensive study of early Irish bells by Cormac Bourke, Ulster Museum, put the Clog Dubh into class one category. These are bronze coated, single sheet, iron bells of quadrangular form with a hooked handle transversely fixed on the crown. It dates from 600 - 900. The Clog Dubh was also known as 'Bearnan Bhrighde', (Tripartite Life) that is the "gapped bell of Brigid" due to its broken state. It is also referred to as 'Clog Geal' (Bright Bell).