The planning permissions on 11 old and dormant quarries in the Brecon Beacons have been revoked to eliminate any risk of them being reopened.
The sites were opened after World War II to meet the need for raw materials in the post-war reconstruction drive.
Most had not been worked for decades and had begun to blend back into the landscape, becoming wildlife havens.
But some had planning permission open until 2042, leaving a risk that the owners could reapply to resume work.
The area's national park authority said it had consulted the sites' owners about approaching the assembly government to have the planning permissions cancelled.
The authority said none of the owners had given any indication of an intention to reopen the disused sites.
Any request to resume quarrying would in any case have raised questions about a site's viability as they would have needed to have met current health and safety and environmental regulations, the authority said.
QUARRIES WITH REVOKED PLANNING PERMISSION
Carreg Dwfn Quarry, Trapp
Brownhill Quarry, Llandybie
Cwar Glas, Llangadog
Part of the River Amman, Rhosaman
Caerhowell Quarry, Penderyn
Danydarren Quarry, Cefn Coed-y-cymmer
Daren (Hillside) Quarry, Llangattock Hillside
Craig-y-gaer Quarry, Clydach Gorge
Darenfelen Crossing (Llanelly) Quarry, Clydach Gorge
Clydach Station Quarry, Clydach Gorge
Hafod Quarry, Brynmawr
Source: Brecon Beacons National Park Authority
The park authority said: "Many quarrying permissions were granted in the years just after the Second World War, when there was a great need for raw materials for the south Wales steel industry.
"Some quarries served a particular need, especially those for silica, found in some strata of the Millstone Grit to make refractory bricks.
"These were used for the linings of blast furnaces in the steel industry.
"Others, like many of the limestone quarries, had already been working for many years and were coming to the end of their economic lives.
"The limestone was burnt for an agricultural fertiliser, and also used in the steel industry, for building stone and general construction work. One of the quarries was specifically a road stone quarry. They have all been closed for many years, indeed decades."
Park Plan Officer Ruth Brown said: "For us there is always a danger that these old quarries, most of which have mellowed into the landscape over time, could be reopened at any time if the operator applies for the approval of modern planning conditions.
"So, we are really very pleased to see these prohibition orders successfully confirmed by the Welsh Assembly Government."