These are sedimentary carbonate materials that accumulate in water as layers or beds through various chemical and biological processes.
Predominantly of calcium and magnesium the chemistry of these carbonates often include other elements such as iron that will play a part in the structure, colour and patterning found in these materials.
A limestone will frequently exhibit structures and other relic features that give clues to the age and environment that existed when the deposit was laid down.
The range of warm beige, golden and burnt sugar colours the result of disseminated iron oxide locally becoming concentrated (mineralisation) in this stone. This is a limestone composed largely from broken fossil shell fragments (bioclasic). The sweeping patterns were created as ocean currents reworked and sorted the loose mineral and fossil fragments on the sea bed.
Travertine is well-known as both a structural and decorative limestone (historically categorized as marble) that has been used since ancient times. It is formed where underground waters have become supersaturated with soluble calcareous minerals as they move up through existing permeable limestone strata. Typically this would be in areas where there is a high geothermal heat gradient associated with volcanic and tectonic activity. On reaching the surface as hot springs the dissolved minerals are deposited often in terraces and as curtains and sheets in this magical environment.