MARBLE (ante). Unstratified statuary marble is white in consequence of the action -to which it has been subjected during some stage of its metamorphism. It is well known that blue limestone when burned becomes white, and this discharge of color will take place even before the carbonic acid gas is expelled. Marbles may be nearly pure •carbonate of lime, or they may contain a large proportion of carbonate of magnesia, in fact, may be matamorphic dolomites (q.v.). The finest statuary marble is worth from $15 to $20 per cubic foot. The Grecian and Italian marbles have been described in the preceding article. In the United States, good statuary marble has for several years been quarried at West Rutland, Vt., where a layer from 3 to 4 ft. thick is interstratified with 40 or 50 ft. of clouded marble. The finest of statuary marble is found at Pittsford, Vt., where there is a bed 20 ft. thick, from which blocks have been taken capable of taking a very fine finish, in some respects perhaps superior to Carrara, although not working with quite equal facility. Some specimens have a, faintish flesh tint, scarcely perceptible, which gives a very fine effect to busts, which, as is well known, are always improved by age, when made of marble too glaringly white. The greater portion of the marble in all quarries is more or less clouded, and most of the ancient temples are built of this kind. The Vermont marbles are of the age of the Trenton limestone, form ing a part of the eolian limestone of prof. Hitchcock, which in that locality is about 2,000 ft. thick. At West Rutland the quarry is from 40 to 60 ft. thick, at Sutherland Falls from 70 to 80, and at Pittsford 600 ft. thick. This marble belt extends n. and s. of ; Rutland co., through Vermont and Massachusetts, but it lose,s in quality in both direc tions. Towards the n. it is finer and harder, but less sound, and towards the s. it becomes coarser. Another belt of white marble extends along the flanks of the Alle ghanies, through a part of Massachusetts, through New York and Maryland, and into Virginia beyond the Potomac river. This marble is a dolomite, and coarsely crystal line. It is quarried at various places in Westchester co., N. Y., and at Baltimore. At
Canaan, Conn., and at Lee, Mass., and other places in New England, good building marble is quarried. Marble from Lee was used for the extension of the capitol at Washington. There are many varieties of colored marbleS, and these are plain or varie,gated. There are plain black, red, blue, gray, and yellow marbles. A jet black marble was used by the ancients. A kind found in Italian ruins is called Nero antico, and is now used for a ground-work for mosaics. Black marbles occur at Derbyshire, England, Kilkenny, Ireland, and at Shoreham, Vt. At Glenn's Falls, N. Y., there is a black limestone, which is used alternately with white marble for tiles, which goes under the name of black marble. The colored marbles were largely used by the Romans and Etruscans for interior decoration. A gray marble much used by the Romans in archi tecture was called eipolino, and had much the appearance of gray granite. The columns of the temple of Jupiter Serapis were constructed of this stone. There are many locali ties of variegated marbles in the United States. A mottled lilac, chocolate, and white, known as Tennessee marble, is regarded with favor for mantels, tables, etc. Another of red, brown, and white is quatTied at Burlington, Vt., but it is rather difficult to work on account of the silica it contains.
The opening of a marble quarry is usually expensive and attended with risk, as it is impossible to determine the quality, of the stone before many feet thickness of rock is removed. From 10 to 30 ft. usually has to be taken off before perfectly sound disin tegrated marble is reached. After a sufficient area of surface has been prepared by the removal of the imperfect stone, channeling machines, which may be either percussion or diamond drills, are set to work, and rectangularly crossed channels are cut to a desired depth, say from 5 to 7 feet. One of the blocks, called the key block, is then broken off at the base by wedging and lifted out with a crane. This gives ready access. to the others, which are then drilled as circumstances may require, broken off by wedging, and removed to a saw-mill, where they are squared or sawed into slabs.