A NEW chapter in the history of Scottish coal mining has been marked with the signing of deals worth almost #450m to supply two of Scotland's main electricity producers.

Mining (Scotland) Ltd, the consortium which took over British Coal's Scottish interests in 1994, yesterday signed contracts worth almost #400m with ScottishPower to supply coal from Scotland's last remaining deep mine at Longannet in Fife over the next six years and from the company's nine opencast sites throughout Scotland over the next five.

In a separate deal, Scottish Hydro-Electric has also concluded an agreement worth #50m to take coal from the opencast sites over the next six years.

The agreements should help to secure the future of Mining (Scotland) Ltd, the Longannet mine, and the company's workforce well into the next millennium.

The deals mark a change in fortune for the deep coal mining industry, which employed about 100,000 at its peak in Scotland around the turn of the century.

Systematic colliery closures since have led to fewer than 1000 being employed in deep mining. Mining (Scotland) Ltd now employs about 800 at Longannet and 850 in open-cast mining.

The ScottishPower deal will allow the development of the Kincardine Reserves, one of the most substantial areas of untapped coal supplies in western Europe, lying under the Firth of Forth, near Longannet.

The Royal Bank of Scotland, which has developed an increasingly close relationship with Mining (Scotland) Ltd in recent years, has agreed to provide lending facilities to finance its business plan. It now acts as its sole banker.

NUM (Scotland) general secretary Nicky Wilson hailed the deals as a ''huge boost'' for Scottish mining, and Scottish Industry Minister Brian Wilson said the agreements were excellent news for the coal and power generation industries which would help secure the future of the Longannet mine, the lifespan of which had been forecast at about three years.

The #400m contract involves the supply of 1.7 million tonnes of coal a year to the ScottishPower-run Longannet power station from the deep mine complex. In a separate contract Mining (Scotland) Ltd's opencast operating arm, Scottish Coal, will provide 750,000 tonnes of coal a year.

Mining (Scotland) Ltd estimates the Kincardine Reserves contain about 80 million tonnes of coal. Mr Alan Houghton, managing director of Scottish Coal (Deep Mine), said about 50% of this had been ''written down'' in case geological problems were encountered, but sai