It forms when
calcium carbonate
precipitates from
hot springs and ground and
surface water solutions.
It has a concentric or
fibrous habit.
By
Al_HikesAZ via Flickr.com
It is naturally white,
but
often
strained brownish, reddish or yellow by impurities such as iron oxides
and others.
By
Frank Kovalchek via Flickr.com
Its main minerals
are calcite
and aragonite.
By
Don Graham via Flickr.com Small organisms such
as
cyanobacteria, algae and others often live on its surface, which causes
the porosity.
By
vtveen via Flickr.com
Like tufa,
it also has
a
siliceous version called siliceous slinter.
By
seier+seier via Flickr.com
It
has been widely used as
building material, both in buildings and
facades, and inside the buildings such as in tiles and floor
installations.
By Darkroom Daze via Flickr.com
Some famous buildings built from this rock are Sacre Coeur in
Paris and Colosseum in Rome.
This site uses British
English, which is the English we use in
Australia.
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