Ice crystals formed under favourable conditions at a sedimentary surface may cause imprints, particularly if the surface contains a relatively high portion of silt. The crystals (and their imprints) start growing as small needles, but continued growth may result in ice flowers. The imprints are optimally visible after complete melting of the ice, but their preservational potential is very small due to easy fluidisation of the water-saturated, silty substratum.