The most valuable and most abundant mineral resource found in Virginia is coal. There are four types: bituminous (soft), anthracite (hard), semi-bituminous and semi-anthracite. The bituminous coal far surpasses the other types in quantity. The coal supply is found primarily in three areas: (1) the Piedmont region--the Richmond Basin and the Farmville area--bituminous; (2) the west side of the Great Valley of Virginia--anthracite and semi-anthracite and (3) the Southwestern Plateau--bituminous and semi-bituminous. The first coal to be mined in the United States was located near Richmond in 1745. At the present time, Virginia ranks sixth in the United States coal production and is believed to have more coal seams now available than any other mining district in the United States. Coal is mined most frequently in Buchanan, Wise and Dickenson Counties. * * * * * Various types of stone resources rank second in financial value of minerals. These include: Calcareous marl (an earthy deposit containing usually lime, clay and sand)--in the Tidewater section--used as a soil neutralizer Cement rock--limestone, marl, shale and clay--in the Coastal Plain and in Augusta, Botetourt, Norfolk and Warren Counties--used in forming portland cement and masonry cement Dolomite (a brittle calcium magnesium carbonate)--in the Valley west of the Blue Ridge Mountains--used as a source of magnesium, for the manufacture of refractories, for building and crushed stone Granite--in the Piedmont and Blue Ridge provinces--used for building monumental stone, crushed stone and paving blocks Greenstone (a dark-green crystalline rock)--in Lynchburg and in the Piedmont area--used for crushed stone and one particular type is used for ornamental stone Limestone--west of the Blue Ridge, in the Appalachian Valley and in the far west of the state--used in the production of lime and for manufacturing chemicals, for cement, as a soil conditioner, for crushed stone and rock wool insulation Marble--in Rockingham, Rockbridge, Scott and Giles Counties--used extensively for monumental stone: jet black, green, white, red, reddish-brown, blue, gray, blue-gray, pink and variegated (different colors within one type); the pink marble is similar to the Tennessee marble and is found primarily in Smyth County Shale (a fragile rock resembling slate)--in the Valley--used in the manufacture of bricks, portland cement and rock wool Sandstone--Oriskany sandstone in Frederick and in Rockingham Counties--chief source for the manufacture of all glass Slate--in Piedmont or eastern slope of the Blue Ridge Mountains, in Albemarle and Buckingham Counties--used chiefly for roofs, baseboards, blackboards, switchboards, sidewalks, flagstones and asphalt shingles