X-ray analyses of JOIDES core samples from the Continental Shelf and Blake Plateau [off Florida] show the presence of a variety of authigenic materials. Calcite is the dominant carbonate mineral in the Eocene and Oligocene sediments. In the Miocene sediments dolomite is the dominant carbonate mineral in the west and calcite in the east. Phosphatic sand is abundant in the Miocene shelf facies. K-feldspar is a major component of the western Eocene limestone residues and clinoptilolite of the eastern Eocene and Oligocene. The Lower Miocene contains an abundance of attapulgite and sepiolite, and the Upper Miocene montmorillonite. The pre-Miocene silicate minerals are believed to be largely authigenic and the post-Oligocene ones largely detrital.