Also found in: Dictionary, Wikipedia.
Related to Jaspilite: chert
a ferruginous quartz, formed as a result of the metamorphism of iron-silica minerals and volcanic deposits. It consists of alternating layers of magnetite and hematite ores and layers of quartz measuring 0.5-3 mm in thickness. In the ore layers the amount of magnetite and hematite is 70-90 percent; in the mixed layers 20-50 percent; and in the nonore layers, 5-10 percent. Depending on the quantity of ore minerals and the degree of dispersion, the layer has a gray, dark gray, bluish, or red coloration. The iron content of jaspilite varies from 20 to 42 percent. The iron content of oxidized jaspilite rises to 66 percent owing to leaching out of quartz and the replacement of magnetite and hematite by martite. Jaspilite is widespread in precambrian beds where it forms large iron ore deposits, for example, at Krivoi Rog and the Kursk Magnetic Anomaly (USSR), Lake Superior (USA), Minas Gerais (Brazil), and Singhbhum (India).