Marble is a name applied to limestones suitable for polishing or ornamental work. Mexican onyx is translucent. Fine marbles are quarried in Italy, Egypt, France, Spain and Greece. Vermont, Georgia, Tennessee and New York supply the greater part of the marble used in the United States. Handsome marbles are imported from Carrara, Italy, and other parts of Europe. Mexican onyx is also imported.
Chalk comes mainly from the south of England. We export some Portland cement and import a little from Europe.
Chalk is of peculiar soft texture; whiting is prepared chalk used to make putty and paints; precipitated chalk is similar.
Lime is made by burning (calcining) common limestones. Portland and hydraulic cements are prepared by calcining siliceous limestones or a mixture of limestone and clay. They are of enormous commercial importance, being used in concrete construction work. Europe and the United States produce large quantities. Pennsylvania is the leading state in this industry.
Buildings (both commercial and residences) are now being extensively constructed of cement—in the former case being re-enforced by iron rods.
Chloride of lime (or bleaching powder), acetate of lime, calcium carbide and many other compounds are of industrial value.
Gypsum (hydrous calcium sulphate) is used in fertilizers. Plaster is prepared by calcining (burning) gypsum. Plaster of paris is its purest form. Alabaster is compact white gypsum. It is a common mineral mined in many parts of the world. Michigan, Kansas, New York, Ohio and other states produce it. Fertilizers and plaster use up large quantities of this mineral. Plaster of paris is used for casts, decorative plaster work, cement, etc.
Fluorite (calcium fluoride) is a less common mineral. Mined in England, Kentucky and Illinois. It is used in chemical manufacture and as a flux for ores.
Phosphate rock (chiefly calcium phosphate) is important in the preparation of fertilizers, and chemicals containing phosphorus. It is found in deposits of organic origin in South Carolina, Florida, Tennessee, the West Indies, Canada, Spain, France, Germany and England.
The natural phosphates are treated with sulphuric acid as a first step in the manufacture of phosphatic fertilizers. Exported in large amount to Germany, England and other countries.