153. Limestone

This name is commonly used to include all stones which contain lime, though differing from each other in color, texture, structure and origin. All limestones used for building purposes contain one or more of the following substances, in addition to lime : Carbonate of magnesia, iron, silica, clay, bituminous matter, mica, talc and hornblende.

There are three varieties of limestone used for building purposes, viz.: Oolitic limestone, magnesian limestone and dolomite.

Oolitic limestones are made up of small rounded grains (resembling the eggs of a fish) that have been cemented together with lime to form a solid rock.

Magnesian limestones include those limestones which contain 10 per cent, and over of carbonate of magnesia.

Dolomite is a crystalline granular aggregation of the mineral dolomite, and is usually whitish or yellowish in color. It is generally heavier and harder than limestone.

All varieties of limestone are liable to contain shells, corals and fossils of marine animals, more or less pulverized. A limestone can be identified by its effervescence when treated with a dilute acid.

Many of our finest building stones are limestones, but as they are less easily and accurately worked than sandstones they are not so largely used except in the localities where the best varieties are found.

The color of limestone is generally a light gray, though it is sometimes a deep blue, and occasionally of a cream or buff color. The light gray varieties often resemble the light, fine-grained granites in appearance.

Most of the granular limestones are susceptible of a high polish.

Good limestone should be of a fine grain and weigh about 145 pounds per cubic foot.

The limestones described below are very durable, but the light-colored stones are apt to become badly stained in large cities, and especially in those cities in which soft coal is used.

All kinds of limestone are destroyed by fire, although some varieties will stand a greater degree of heat without injury than others.

154. Description of Limestones

The limestones most extensively used for building purposes come from the States of Illinois, Indiana, Ohio, New York and Kentucky.

The most celebrated American limestone is that quarried at Bedford, Indiana, which is a light-colored oolite, consisting of shells and fragments of shells (so minute as to be scarcely discernible by the naked eye), cemented together by carbonate of lime.

This stone is most remarkably uniform in grain and texture, is exceedingly bright and handsome in color, and is less liable to discolor than most light stones.

It is equally strong in vertical, diagonal and horizontal directions, and when first quarried is so soft as to be readily worked with a saw or chisel; it hardens, however, on exposure, and attains a strength of 10,000 to 12,000 pounds per square inch. Owing to its fine and even grain and ease in cutting in any direction, it is especially adapted for fine carving. The stone is also very durable.

On account of its many excellent qualities it was selected by the architect for Mr. George W. Vanderbilt's palatial residence at Biltmore, N. C. The Auditorium Building at Chicago, the Manhattan Life Building, New York; the mansion of Mr. C. J. Vanderbilt on Fifth Avenue, New York; the State House at Indianapolis and many other prominent buildings are built of this stone. There are several quarries of this stone, the products varying somewhat in color and quality.

A gray limestone is quarried at Lockport, N. Y., which is extensively used for trimmings in that State and some parts of New England.

There are large quarries of limestone at Dayton and Sandusky, Ohio; Joliet, Grafton and Chester, Illinois, and in the vicinity of Topeka, Kansas. There are several small quarries which supply the local demand in various parts of Kansas. The Topeka stone can be worked almost as easily as wood, and yet becomes hard and durable when placed in the building.

At Carthage, Jasper County, Missouri, there are extensive quarries of limestone, "which produce large quantities both of quicklime and building stone. The stone is coarse grained and crystalline, takes a good polish, and is well adapted to exterior finishing.

Excellent quarries of limestone also exist at Phoenix, Missouri, the stone being shipped to St. Louis, Kansas City and Omaha.

Kentucky. - This State also contains a great quantity of fine limestone, some varieties of which are said to be equal, if not superior, to the Bedford stone. The best known of the Kentucky limestones is probably the Bowling Green (oolitic) stone, quarried at Memphis Junction. This stone is almost identical in composition with the celebrated " Portland " stone of Great Britain. Its color is light gray. It is as readily worked as the Bedford stone, is very durable, and is pre-eminent in its resistance to the discoloring influences of mortar, cement and soil.