A Bay of Plenty iwi wants visitors to leave its precious volcanic glass alone.
Tuhua (Mayor Island) is known for its rich veins of obsidian, also known as tuhua by Maori.
Magda Williams from the Tuhua Trust Board says the obsidian is tapu (sacred) to the island's traditional owners.
She says a helicopter company operating tours to the island has been asked to return the sacred rock.
Now the obsidian is no longer used for cutting tools or weapons, the only reason for taking it is to place in cemeteries and marae to link the deceased back to the island, she says.
Ms Williams says the iwi's kuia and kaumatua are upset that the non-Maori visitors take "big chunks" of the rock for doorstops or garden ornaments.
