For what is this Rock used?
On account of its great hardness, it is used for large public structures, as bridges, churches, &c. The ancient temples and other buildings in Egypt, Asia, and Italy, were built of different colored granites, especially the beautiful Oriental red granite.
What is Slate?
The common name for a bluish fossil stone, very soft when dug out of the quarry, and easily cut or split into thin plates,—a property which renders it invaluable for a variety of purposes.
Invaluable, extremely valuable.
For what is it used?
Slate has superseded the use of lead for covering roofs, even of the largest buildings; being lighter and more durable, it is preferable to tile: it is also employed for slabs to form cisterns, shelves for dairies, and other purposes, on account of its strength, coolness, and the ease with which it can be cleaned; the latter quality renders it also of great value in the business of education, as a cheap substitute for paper. The ancients were unacquainted with the use of slate.
What other kinds of stone are used in building?
Limestone, or the calcareous rocks of the geologist: of these there are many varieties. Those which are easily cut and polished are termed marbles, and are used in sculpture and in ornamental architecture. The coarser marbles are used for the common purposes of building.
Calcareous, partaking of the nature of calx or lime,—a term employed to describe chalk, marble, and all other combinations of lime with carbonic acid.