Chert & phosphorite in the Permian of Wyoming, USA. The Permian-aged Phosphoria Formation has a significant component of phosphorite, a scarce, phosphate-rich sedimentary rock. This material is mined in southern Idaho as a source of phosphorus for the fertilizer industry, the fireworks industry, and other uses. Phosphorites are generally considered to have >15-20% phosphate content. Texturally, phosphorites can be obviously granular, with fossil fragments or oolites or peloids or lithic fragments, or they can be composed of extremely fine-grained, phosphate-rich mud. Compositionally, the phosphate component in phosphorites is principally a mix of apatite minerals: chlorapatite (Ca5(PO4)3Cl), fluorapatite (Ca5(PO4)3F), hydroxyapatite (Ca5(PO4)3OH)), and carbonate fluorapatite (Ca10(PO4,CO3)6F2-3). Phosphorites are generally marine sedimentary rocks. They range in age from Precambrian to Holocene. In modern oceans, they tend to occur along the eastern margins of some ocean basins where deep-water upwelling occurs under areas of high biologic productivity. Stratigraphy: Rex Chert Member over Meade Peak Member, Phosphoria Formation, Roadian Stage to Wordian Stage, lower Guadalupian Series, mid-Permian Locality: roadcut on the northern side of Route 26/Route 89 at the town of Astoria Hot Springs, Snake River Canyon, southern Teton County, northwestern Wyoming, USA