SANDSTONES. Sandstones (q.v.) are composed of rounded and angular grains of sand, so ce mented and compacted as to form a solid rock. The cementing materials are silica, oxide of iron. and carbonate of lime. Silica cement gives a white colored stone, very firm and durable, but difficult to work: oxide of iron cement gives a brownish or reddish stone of fair durability and fairly easy to work: and carbonate of lime gives a grayish stone soft and easy to work, but less durable than when either of iron or silica forms the cementing material. Some sandstones have a clayey cement. is more objection able than any of the others, and other sand stones contain little, if any, cement. owing their to the pressure under which they were consolidated. Often the cemented grains com prise feldspar and mien, as well as sand. The texture of sandstones varies from exceedingly tine-grained stones to those composed of pebbles of various sizes. The latter are called conglinn
erates if the grains are rounded, and hreeeias if they are angular. Sandstones vary in color: gray. buff. drab, blue, brown, pink, and red being the (.olors of well-known varieties. Sa 11d:41.011es generally are softer when quarried than after a period of seasoning.
(loud sandstone for' structural purposes is finite] so widely distributed in the United States that it is ionpossible to mention all of the notable deposit:. The Berea stone. of Ohiat the Medina stone and Milestone. of New York: the Portland slime. of Connectieut and Massachm setts; and the red and brown sandstones. of New Jersey, are the most extensively quar ried and best known. Of the foreign sandstones the variety is quite as great as in the Sta tes.