Portal tombs, sometimes called dolmens, are among the most recognisable of Ireland's prehistoric structures: typically two tall upright portal stones at the entrance, a back stone, and a large capstone tilted at an angle overhead, the whole arrangement once covering a burial chamber. They were built by farming communities in the fourth or third millennium BC, and Mayo has a notable concentration of them.

The principal scholarly record for this structure comes from Ruaidhrí de Valera and Seán Ó Nualláin, whose Survey of the Megalithic Tombs of Ireland, Volume II, covering County Mayo, was published by the Stationery Office in Dublin in 1964. De Valera and Ó Nualláin spent years systematically documenting megalithic monuments across the country, and their Mayo volume remains a foundational reference for the county's prehistoric archaeology. The survey gave researchers and later generations a baseline record of what existed, where, and in what condition, at the time of documentation.

Beyond what the 1964 survey recorded, the specifics of this particular tomb's current condition, dimensions, or accessibility are not well documented in the available sources, so it would be unwise to describe the site in detail that cannot be verified. What can be said is that An Gort Breac Thuaidh sits within a county whose boglands and hill slopes have preserved megalithic monuments in varying states, some dramatically upright, others collapsed or partially buried, and that finding any of them often involves a closer reading of the landscape than a casual visitor might expect.