beds, minerals, layers, structures, rocks, sandstones, limestones, shales, mineral, clays, smectite, bands, sand, shale, deposits, structure, material, sandstone, masses, seams, clay, limestone, silicates, mixtures, bed, systems, sands, marls, drift, sediments, tuffs, vermiculite, sheets, greenstone, lavas, particles, units, porphyries, materials, plates, conglomerate, slates, gravel, phase, phases, trap, mica, basalt, traps, flints, matters, conglomerates, series, mixture, species, illite, silts, deposit, zones, flows, chlorite, marble, carbonates, quartz, smectites, ash