As the coal mining industry declined, so did the general importance of domestic mining to the whole economy. Only 0.2% of the labour force was engaged in mining operations in 1988 and the value added from mining was about 0.3% of the total for all mining and manufacturing. Domestic mining production supplies an important quantity of some nonmetals: silica sand, pyrophyllite clay, dolomite, and limestone. Domestic mines are contributing declining shares of the country's requirements for some metals: zinc, copper, and gold. Almost all of the ores used in the nation's sophisticated processing industries are imported.