Stones depend much on the adhesive qualities of the material cementing their component parts. The strength of these cementing materials determines their resistance to crushing and also to the effects of weather. It is important, therefore, to select a stone of a not too friable nature, and one that presents a clean bright fracture when freshly broken, with the cementing material closely embracing the various constituents of the specimen.

Resistance To Crushing

The stone to be tested should be of a fairly large section, say 4 to 6-inch cubes. The weight should be applied evenly over the surface, and gradually increased.

Absorption

Well dry the specimens and immerse them in water for a day or more. Weigh both before and after placing them in the water. The difference will represent the amount the stone will have absorbed.

Soluble Matter In Stone

The immersion of small chippings of the stone in water for several hours will serve as a test for the presence of alumina or other soluble matter therein. Should the water become cloudy on shaking the presence of deleterious substances may be presumed, and if the cloudiness be pronounced the stone should be rejected.

Frost

For resistance to the action of frost a careful inspection of the exposed stone in the quarries will give a fair criterion whereon to rest one's judgment, or the examination of a building in which the stone in question has been exposed for some years is even more reliable.

Foul Air

For resistance to the action of the foul atmosphere of large towns, the treatment of the stone by immersion for some time in a weak solution of sulphuric acid in water will give some idea as to its power of resisting the action of sulphurous fumes, etc., in the air or charged in the rain.