sentences:  The district suffered greatly from the fall in the price of silver in 1893, and remained moribund until World War I, when the manganese deposits of the district became valuable, and Philipsburg became one of the top US producers of that metal.Silver occurs in veins filling fracture zones through Paleozoic limestone.Minerals in the silver-ore veins include polybasite, pyrargyrite, proustite, sphalerite, galena, and tennantite.