TRAVERTINE
from Oklahoma
Classified as a sedimentary, crystalline rock.
Consisting of almost pure calcium carbonate, travertine may also contain some detrital quartz and clay. Travertine is a very light coloured rock, unless it contains iron compounds or other impurities, which can give it colouring. Travertine deposits are rounded, botryoidal (resembling a grape structure) and often banded structures. The rock is formed of small crystals of calcite which bind together other sediment particles. In many situations travertine occurs in strata. The rock is often bedded.
Travertine is frequently associated with springs rising from deep-seated sources. This results in many hot springs, especially in volcanic regions, giving rise to travertine by the deposition of solid calcium carbonate.