Its bed is composed of calcareous tufa, chiefly the remains of reeds and mosses, forming a beautiful succession of cascades.
The fossil bones which lie in the calcareous tufa of this region will yet, we hope, reveal the ancient fauna.
The calcareous tufa seems to be the most recent rock formed.
It is in this calcareous tufa alone that fossil animal remains have yet been found.
One spring of copious flow is a pool within a capacious dome-shaped cavern, hollowed 491 out of a mound of calcareous tufa.
It's calcareous tufa I'm a-wearing, wove on me by exudation and accretion in the past two thousand years.
We walked to the borders on a mass of calcareous tufa, and we saw that this substance had even encrusted the reeds on the shore.
The exterior was entirely of calcareous tufa of Tivoli, called travertine, a fine hard and white stone.