Calcareous sinter is characterised by laminations of prismatic crystals growing perpendicular to the substrate; laminations are separated by thin layers of microcrystalline carbonate. Calcareous sinter is porous due to the calcareous crystals enclosing many small cavities. Macrophytes are absent, consequently porosity is very low. Exclusion of species is due either to high temperature (travertine), high pH/ionic strength (tufa) or absence of light (speleothems). 
Pedley (1990) suggests the term be abandoned in favour of tufa for ambient temperature deposits. This avoids any potential confusion with siliceous sinter and prevents deposits formed in different environmental conditions (hot spring deposits, cold spring deposits and speleothems are all lumped together under the term sinter) from being amalgamated into one group.