Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/557

Rh M A II B L E 520 i.i Derbyshire. From Ashford is also derived a very beautiful stone known as rosewood marble. This is a dense brown laminated limestone, displaying when polished a handsome pattern somewhat resembling the grain of rosewood ; it occurs in very limited quantity, and is used chieily for inlaid work. With the rosewood marble may be compared the well- known landscape marble or Gotham stone, an argillaceous limestone with peculiar dendritic markings, due probably to the infiltration of water containing oxide of manganese. This limestone occurs in irregular masses near the base of the White Lias, or uppermost division of the Rhretic series. It is found principally in the neighbourhood of Bristol. The arborescent forms depicted in bluish-grey upon this landscape marble form a marked contrast to the angular markings of warm brown colour which are seen on slabs of ruin marble from Florence a stone occasionally known also as landscape stone, or pietra paesina. British limestones of Secondary and Tertiary age are not generally compact enough to be used as marbles, but some of the shelly beds are employed to a limited extent for decorative purposes. Ammonite marble is a dark brown limestone from the Lower Lias of Somersetshire, crowded with ammonites, principally A. planicostata. Under the name of Forest marble, geologists recognize a local division of the Lower Oolitic series, so named by W. Smith from Wychwood Forest in Oxfordshire, where shelly limestones occur ; and these, though of little economic value, are capable of being used as rough marbles. But the most important marbles of the Secondary series are the shelly limestones of the Purbeck formation. Purbeck marble was a favourite material with mediaeval architects, who used it freely for slender clustered columns and for sepulchral monuments. It consists of a mass of the shells of a fresh-water snail, Paludina carinifera, embedded in a blue or grey limestone, and is found in the Upper Purbeck beds of Swanage in Dorsetshire. Excellent examples of its use may be seen in Westminster Abbey and in the Temple Church, as well as in the cathedrals of Salisbury, Winchester, Worcester, and Lincoln. Sussex marble is a very similar stone, occurring in thin beds in the Weald clay, and consisting largely of the shells of Paludina, principally P. sussexiensis and P. Jluviorum. The altar stones and the episcopal chair in Canterbury cathedral are of this material. Mixtures of limestone and serpentine frequently form rocks which are sufficiently beautiful to be used as orna mental stones, and are generally classed as marbles. Such serpentinous limestones are included by petrologists under the term ophicalcite. The famous verde antico is a rock of this character. Mona marble is an ophicalcite from the metamorphic series of the Isle of Anglesey, while the &quot; Irish green &quot; of architects is a similar rock from Connemara in western Galway. It is notable that some of the &quot; white marble&quot;cf Connemara has been found by Messrs King and Rowney to consist almost wholly of malacolite, a silicate of calcium and magnesium. A beautiful marble has been worked to a limited extent in the island of Tires, one of the Hebrides, but the quarry appears to be now exhausted. This Tiree marble is a limestone having a delicate carnelian colour diffused through it in irregular patches, and containing rounded crystalloids of sahlite, a green augitic mineral resembling malacolite in composition. When dissolved in acid the marble leaves a brick-red powder, which has been studied by Dr Heddle, who has also analysed the sahlite. Many marbles which are prized for the variegated pat terns they display owe these patterns to their formation in concentric zones, such marbles being in fact stalagmitic deposits of carbonate of lime, and probably consisting in j many cases of aragonite. One of the most beautiful stalagmitic rocks is the so-called onyx marble of Algeria. This stone was largely used in the buildings of Carthage and Rome, but the quarries which yielded it were not known to modern sculptors until 1849, when M. Delamonte rediscovered the marble near Oued-Abdallah. The stone is a beautifully translucent material, delicately clouded I with yellow and brown, and is greatly prized by French workmen. Large deposits of a very fine onyx-like marble, I similar to the Algerian stone, have been worked of late years at Tecali, about 35 miles from the city of Mexico. Among other stalagmitic marbles, mention may be made of the well-known Gibraltar stone, which is often worked into models of cannon and other ornamental objects. This stalagmite is much deeper in colour and less translucent than the onyx marbles of Algeria and Mexico. A richly tinted stalagmitic stone worked in California is known as Californian marble. It is worth noting that the &quot;ala baster &quot; of the ancients was stalagmitic carbonate of lime, and that this stone is therefore called by mineralogists &quot; Oriental alabaster &quot; in order to distinguish it from our modern &quot; alabaster,&quot; which is a sulphate, and not a car bonate, of lime. The brown and yellow colours which stalagmitic marbles usually present are due to the presence of oxide of iron. This colouring matter gives special characters to certain stones, such as the giallo antico, or antique yellow marble of the Italian antiquaries. Siena marble is a reddish mottled stone obtained from the neighbourhood of Siena in Tuscany; and a somewhat similar stone is found in King s County, Ireland. True red marble is by no means common, but it does occur, of bright and uniform colour, though in very small quantity, in the Carboniferous lime stone of Derbyshire and north-east Staffordshire. It may be noted that the red marble called rosso antico is often confounded with the porfido rosso antico, which is really a red porphyritic felstone. Fire marble is the name given to a brown shelly lime stone containing ammonites and other fossil shells, which present a brilliant display of iridescent colours, like those of precious opal. It occurs in rocks of Liassic age at the lead-mines of Bleiberg in Carinthia, and is worked into snuff-boxes and other small objects. By mineralogists it is often termed lumackella, an Italian name which may, i however, be appropriately applied to any marble which i contains small shells. It would unnecessarily extend this article to enumerate the local names by which marble- workers in different countries distinguish the various stones which pass under their hands. The quarries of France, Belgium, and Italy, not to mention less important localities, yield a great diversity of marbles, and almost each stone bears a distinc tive name, often of trivial meaning. America possesses some valuable deposits of marble, which in the eastern States have been extensively worked. The crystalline limestones of western New England furnish an abundance of white and grey marble, while a beautiful material fit for statuary work has been quarried near Rutland in Vermont. A grey bird s-eye marble is obtained from central New York, and the greyish clouded limestones of Thomaston in Maine have been extensively quarried. Of the variegated and coloured marbles, perhaps the most beautiful are those from the northern part of Vermont, in the neighbourhood of Lake Champlain. A fine brecciated marble is found on the Maryland side of the Potomac, below Point of Rocks. Among the principal localities for black marble may be mentioned Shoreham in Vermont and Glen Falls in New York. In_ Canada the crystalline limestones of the Laurentian series yield beautiful marbles. XV. 67