Editing Limescale (section)

==As a stone==
The Roman [[Eifel Aqueduct]] was completed around 80 AD and broken and largely destroyed by Germanic tribes in 260. By the Middle Ages the limestone-like limescale accretions from the inside of the aqueduct were particularly desirable as a building material, called "Eifel marble" in an area with little natural stone. In the course of operation of the aqueduct, many sections had a layer as thick as {{convert|20|cm|in|0}}. The material had a consistency similar to brown [[marble]] and was easily removable from the aqueduct. Upon polishing, it showed veins, and it could also be used like a stone board when cut flat. This artificial stone found use throughout the Rhineland and was very popular for [[column]]s, window frames, and even [[altar]]s. Use of "Eifel marble" can be seen as far east as [[Paderborn]] and [[Hildesheim]], where it was used in the [[cathedral]]s. [[Roskilde Cathedral]] in [[Denmark]] is the northernmost location of its use, where several gravestones are made of it.<ref>{{cite book |last1=Tegethoff |first1=F. Wolfgang|last2=Rohleder |first2=Johannes |last3=Kroker |first3=Evelyn |url=https://books.google.com/books?id=pbkKGa19k5QC&dq=%22eifel+aqueduct%22&pg=PA93 |title=Calcium Carbonate: From the Cretaceous Period Into the 21st Century |work=Birkhäuser |year=2001 |publisher=Springer |isbn=3-7643-6425-4}}</ref>

Trade to the west took it to England as a high-status export material in the 11th and 12th centuries, where it was made into columns for a number of [[Norman architecture|Norman]] English Cathedrals. The impressive polished brown stone was known for many years as 'Onyx Marble'. Its origin and nature was a mystery to people studying the stonework at [[Canterbury Cathedral]], until its source was identified in 2011.<ref>{{cite book| author=C. Wilson|year=2015| chapter=Canterbury Cathedral's Mystery 'Marble': A Double Imposture Unmasked' |pages=156–60| editor= P. Fergusson| title=Canterbury Cathedral Priory in the Age of Becket |location=New Haven and London |isbn=9780300175691 }}</ref> It is used there as columns supporting the cloister roof, alternating with columns of Purbeck Marble. These large cathedral cloisters needed several hundred such columns around an open quadrangle, which must have been supplied by a well-organized extraction and transport operation. The Eifel deposits, now called [[Calcareous sinter]] or calc-sinter (since it is neither [[onyx]] nor [[marble]]), have also been identified at [[Rochester Cathedral|Rochester]]<ref>{{cite journal| author=John McNeill| title=The Romanesque Cloister in England| journal=Journal of the British Archaeological Association| volume=168 |year=2015|pages=34–76| doi=10.1179/0068128815Z.00000000038| s2cid=194154048| url=https://www.academia.edu/19984110}}</ref> and in the now lost [[Norman architecture|Romanesque]] cloister at [[Norwich Cathedral|Norwich]]<ref>{{cite journal|author= R.B. Harris| year=2019| title=Reconstructing the romanesque cloister of Norwich cathedral | journal=The Antiquaries Journal| publisher=Cambridge University Press| volume=99|pages=133–159| doi=10.1017/S0003581519000118| s2cid=203298501}}</ref> as well as the Infirmary Cloisters, Chapter House windows, and Treasury doorway at Canterbury.<ref>{{cite web|url=http://www.canterbury-archaeology.org.uk/stones-calc/4594124807| title=calc-sinter or Onyx Marble| author=Geoff Downer|year=2019|website=canterbury-archaeology.org.uk| publisher=Canterbury Historical & Archaeological Society (CHAS)}}</ref>