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tufa-limestone

tufa-limestone

SRI Petrography ID: 58

Plainfeld
Salzburg

Names

[de] Tuff Kalkstein
[en] tufa-limestone

Description

Tufa is a highly porous, sedimentary rock (limestone) composed of calcium carbonate, CaCO3. It is formed by biological and chemical precipitation of Calcite or aragonite from cold, supersaturated surface or ground waters. Mostly the metabolism of algae, bacteria and mosses is important for tufa formation due to consumption of CO2 (causing CaCO3 supersaturation). Tufa is mostly of brown colour due to impurities (mainly iron oxides).
Also speleothems (flowstones, stalagmites, stalaktites,...) are formed in a similar way but without biological impact.
Fresh tufa often contains remains of trees, branches, leaves, fossil one their moulds.

Color

usually brown or yellow, sometimes red-brown

Grain Size

fine grained

Texture

porous

Minerals

calcite, aragonite, containing organic material, clay, quartz, iron oxides

Occurences

various sites, esp. alps

Comments

Tufa was often used for walls, esp. Corner stones and architectural elements, due to ist easy workability.

Classification

Class

SEDIMENTARY ROCKS

Broader Terms

carbonate sedimentary rocks