Mass rocks of Ireland

A mass rock (carraig an Aifrinn) was a rock used as an altar for Mass in the 17th and 18th centuries, when Catholic worship in Ireland was outlawed or restricted: after Cromwell's campaign and under the Penal Laws, bishops were banished, priests had to register under the Registration Act 1704, and priest hunters were sometimes employed to arrest them. Isolated places were chosen for the gatherings. Some mass rocks are still places of pilgrimage with open-air Masses, and services were offered or proposed at several in 2020, when indoor gatherings were restricted during the COVID-19 pandemic. (Wikipedia, "Mass rock" ↗)

Many of these records rest on local tradition, which the surveyors write down as they heard it ("according to local information", "locally known as"). That is how the record works for this kind of site: it notes where a community remembers Mass being said, not proof of every date. Some records describe an older monument taken into use: one in Ballymihil, Co. Clare, is a wedge tomb that "may have been reused as a Mass-rock" (CL005-310 ↗).

Mass-rock records in the Republic, by county. Separately, the record has 44 sites classed as "Penal Mass station", listed below under their counties, and 8 "present location" records for stones that have been moved.

Open a county for every record: townland, a line quoted from the survey's own description where it has one, the SMR number (linked to the Historic Environment Viewer) and a map link where the record has a position.

• A record is a survey entry, not a promise that something is there. The Sites and Monuments Record lists sites that are known, reported or marked on old maps, including some that have been destroyed, moved, or were never found when inspected. Each record's own description says what the surveyors saw; read it before you set out.
• A present location record is where a moved object (in a church, a museum, a school, a garden) is now. The place it was found or first stood usually has a record of its own, so one object can appear twice.
• Some records have no description uploaded yet, and a few have no usable position; they are marked as such.
• Most sites are on private land. Ask before you cross a field, and leave things as you find them: monuments in the Record of Monuments and Places are protected under section 12 of the National Monuments (Amendment) Act 1994 ↗.
• The Sites and Monuments Record covers the Republic only. Northern Ireland's record (the NISMR) is counted here by county from its open data, by matching the record descriptions; it is not listed site by site and its counts are not directly comparable.
• Northern Ireland: 45 NISMR records mention a mass rock (including possible, removed and unlocated ones); the NISMR also has separate "Mass site" and "Penal site" records, not counted here.

Source: National Monuments Service, Archaeological Survey of Ireland, Sites and Monuments Record, open data via data.gov.ie ↗ (CC BY 4.0); every record links to the Historic Environment Viewer ↗. Northern Ireland: Northern Ireland Sites and Monuments Record (Department for Communities, Historic Environment Division), OpenDataNI ↗.