title: Glauconite from the Precambrian Belt Series, Montana.
abstract: Glauconite from the upper part of the Missoula Group of the Belt Series, Flathead County, Montana, has been dated at 1070 million years by potassium-argon and rubidium-strontium analyses. This is the first glauconite of Precambrian age reported in North America.
authors.forename: R A
authors.initials: RA
authors.lastname: Gulbrandsen
authors.forename: S S
authors.initials: SS
authors.lastname: Goldich
authors.forename: H H
authors.initials: HH
authors.lastname: Thomas