The only Irish clachan settlement outside of Ireland and Britain has been found in South Australia's Mid North, an archaeological researcher says.

Key points: Most Irish people lived in informal settlements called clachans until the mid-19th century

Most Irish people lived in informal settlements called clachans until the mid-19th century Archaeologists have uncovered a clachan in South Australia

Archaeologists have uncovered a clachan in South Australia SA is known as the "least Irish state" because of its lack of convicts

The cluster of houses dating back to the 1850s had been hidden under a field about 1 kilometre from the town of Kapunda for about 70 years.

Radar and then excavation confirmed the settlement — known as Baker's Flat — was built in the style of a traditional Irish clachan.

Clachans are informal clusters of up to 30 to 40 farmhouses and outbuildings surrounded by farmland.

Irish-Australian Flinders University archaeologist Susan Arthure revealed the discovery in an Archaeological and Anthropological Sciences journal article published with three other academics.

She said clachans were the most common form of settlement Irish people lived in until the middle of the 19th century, but by the early 20th century there were "virtually no clachans left in Ireland".

The remains of a house at the clachan discovered near Kapunda. ( Supplied )

However, people continued to live at the Baker's Flat clachan near Kapunda well into the 1900s, long after they had disappeared in their home country.

A second house at the Baker's Flat clachan. ( Supplied )

Ms Arthure said it was the only clachan definitively found outside Ireland, however there were "hints that there is maybe one" in the United States.

"It's never been seen before in Australia," Ms Arthure said.

"Which is not to say they don't exist in Australia, but nobody has ever seen one before in Australia — nobody has ever identified one.

"So it's significant because people came from another country, they colonised in South Australia, but they kept on doing what they had done before given the opportunity to have that land, and it's quite exciting because we haven't seen it outside of Ireland until now."

A clachan at Coolanlough in Ireland. ( Wikipedia: Bob Embleton )

Traditional farming techniques used

Kapunda, just north of the Barossa Valley, was established in 1842 after copper was discovered in the area.

Archaeologist Kelsey Lowe with a magnetic gradiometer at the site of the clachan. ( Supplied: Flinders University )

While most of the miners were Cornish, some Irish people also came to South Australia at the same time because of the potato famine.

A group of Irish settlers bought about 60 hectares of land, which they ran as a "rundale", another common practice in Ireland at the time where a group of people would decide together where and when to run livestock and grow crops on their land.

Ms Arthure said they were not rich "by any means" but they lived sustainably together in a traditional way for 100 years.

Up to 500 people lived there at one time.

The remains of any houses still there in the 1950s were demolished for farming.

"The Baker's Flat community had, in effect, disappeared from both local memory and the landscape," Ms Arthure, Kelsey Lowe, Lynley Wallis and Josh Feinberg wrote in their journal article.

As well as several houses, they also found a dance floor mentioned in the Southern Cross Catholic newspaper as "hard as cement from the thousands of feet that gaily 'kept the time' to the piper's or fiddler's tune".

Radar confirmed location of buildings

Ms Arthure had heard about a missing Irish settlement but could only find less than a page worth of anecdotes about it.

She found court records describing how people in the area were living, which she thought sounded similar to clachans she knew about from Ireland.

The only official map of the settlement Ms Arthure found from 1893 led her to its location.

Photos published in a newspaper in 1906 showing what it called the "old-time village" at Baker's Flat. ( Supplied: Susan Arthure )

In 2013, she found ceramics and glass in the area, and then ground-penetrating radar gave them even more confidence she was looking in the right area.

Only a few similar geophysical surveys have ever been conducted in Australia, including at Tasmania's Port Arthur.

Susan Arthure with household artefacts found at the site. ( Supplied: Flinders University )

"The results showed up rectangular features, they showed up fences, they showed up old pathways and [in 2016 and 2017] we excavated an Irish house with all of the types of things that people in the 19th century used," Ms Arthure said.

She said the discovery was also interesting because South Australia was "the least Irish of all the states of Australia" because it never had convicts.

"Irish people are good at moving to other places and creating a life there very successfully," she said.

"For me, it's significant that they came to South Australia, they created good lives or sustainable lives and they still maintained their own identity as well.