Green Earth,

Green Earth, a mineral of a green colour and earthy character, often found filling or lining the vesicular cavities of crystalline igneous rocks, sometimes also disseminated through highly decomposed basic eruptive rocks, in which it is evidently a product of the alteration of such minerals as pyroxene, amphibole, biotite, &c. It consists principally of silica, alumina, magnesia, and protoxide of iron, the silica constituting about one-half. There are probably several minerals included under the 'green earth' of such igneous rocks. Some of these closely resemble Serpentine (q.v.) and others Chlorite (q.v.), in their general appearance.—Glaucinite is the name given to the green earth which is not infrequently met with in sedimentary rocks, such as some of the sandstones in the Cretaceous system. In such rocks glauconite occurs in the form of grains, which in many cases are casts of minute shells. The same material has been met with in the shells of recent rhizopods and in fragments of coral dredged up in deep water. There is also a green earth used as a pigment by painters in water-colours, who know it by the name of Mountain Green. For their use it is mostly brought from Monte Boldo, near Verona, and from Cyprus.