Siltstone is one of many otherwise unremarkable sedimentary layer stones.
 In Real Life
Siltstone is a type of clastic sedimentary stone, in which the grains range in size from 1/16th of a millimeter to 1/256th of a millimeter. Stones comprised of grains larger than 1/16th of a millimeter are called Sandstones, while stones comprised of grains smaller than 1/256th of a millimeter are called Mudstones.
[INORGANIC:SILTSTONE] [USE_MATERIAL_TEMPLATE:STONE_TEMPLATE] [STATE_NAME_ADJ:ALL_SOLID:siltstone][DISPLAY_COLOR:6:7:0][TILE:'%'] [SEDIMENTARY] [IS_STONE]