"Iron-grainstone"@en . "FEGST"@en . "stable"@en . . "Iron-grainstone"@en . "Iron-grainstone - A type of ironstone, classified on the basis of its depositional texture. It is a grain-supported ironstone with little matrix (mud-grade material smaller than 32 µm). British Geological Survey Research Report RR/99/03, section 5.2, table 14 and fig. 9."@en . . .