At 10 years old, Martin cannot read, but he is an old hand at detecting traces of the gold he and his young cousins dig for at an open-pit mine in southeastern Venezuela.

In the town of El Callao, extracting gold from soil starts as a kid's game, but soon becomes a full-time job that human rights activists slam as dangerous exploitation.

Small and agile, the children's size helps them shimmy into narrow wells to hack out muddy earth, hoping it will contain gold — which has become ever more precious as Venezuela's oil production has plummeted.

Doubled over, they carry heavy bags of earth under the relentless sun to murky puddles of water where they rinse it in wooden trays.

Martin explains that "whatever is gold gets stuck to the mercury," a poisonous and environmentally toxic substance they use for its ability to extract gold from ore.

He is one of around a thousand children in the region involved in illegal gold mining, a booming industry in the resource-rich country that has been battered by multiple economic crises.

'A matter of survival'

Martin — not his real name — lives in El Peru, a nearby hamlet. He has never been to school.

Carlos Trapani of the Cecodap children's rights NGO told AFP that the backbreaking work and its associated dangers have become "normalized" in these communities.

Despite what Trapani describes as "the worst conditions," Martin says he "would rather get gold than go to school."

"My dad says that money comes from work," he told AFP, in an interview granted with the consent of his parents.

"With the money I earn here I buy my things: shoes, clothes, sometimes some sweets."

Around a thousand children are working in illegal mines in the region, according to the private Catholic university UCAB in neighboring Guyana.