Environment Minister Tony Burke is set to reveal his decision on heritage listing for Tasmania's Tarkine.

The federal government has been assessing the heritage value of Tarkine, home to the largest tract of temperate rainforest in the southern hemisphere and the last haven of disease-free Tasmanian devils.

Mr Burke will make an announcement in northern Tasmania on Friday.

Environmentalists want the area protected from mining.

They say it fulfils eight of 10 criteria for becoming a world heritage area - only the second place in the world that would do so - but only five per cent is protected in national parks.

The Tarkine been home to mining for more than a century and 10 new mines, some open-cut, are planned for the area in the next five years, according to the Tarkine National Coalition.

The state government has granted several mining leases, which are still subject to federal approval, and Tasmanian Premier Lara Giddings says only one per cent of the Tarkine will be affected by the proposals.

In 2010, Mr Burke allowed an emergency heritage listing in the area to lapse.