Authigenic albite occurs as the major mineral constituent in a prominent tuff in the upper part of the Tipton Member of the Eocene Green River Formation in Wyoming. Minor amounts of analcime and quartz are associated with the albite, and the tuff is enclosed in rich oil shale. Authigenic albite and K-feldspar as crystal aggregates and subhedral to euhedral crystals, mostly less than 10 μm in size, are ubiquitous minor constituents in oil shale in the Piceance Creek basin, Colorado. In terms of their intermediate structural state and cell parameters, these authigenic albites are similar to synthetic albites. The K-feldspars are disordered and similar to those reported for other closed-basin deposits.