Saint Illidius was a 4th century bishop of Clermont, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. To Illidius is attributed the rise of Clermont-Ferrand

Clermont-Ferrand

Clermont-Ferrand is a city and commune of France, in the Auvergne region, with a population of 140,700 . Its metropolitan area had 409,558 inhabitants at the 1999 census. It is the prefecture of the Puy-de-Dôme department...

 as a center of religious teaching and culture. According to tradition, he cured the daughter of the Roman Emperor Magnus Maximus

Magnus Maximus

Magnus Maximus , also known as Maximianus and Macsen Wledig in Welsh, was Western Roman Emperor from 383 to 388. As commander of Britain, he usurped the throne against Emperor Gratian in 383...

 at Trier

Trier

Trier, historically called in English Treves is a city in Germany on the banks of the Moselle. It is the oldest city in Germany, founded in or before 16 BC....

.

Gregory of Tours

Gregory of Tours

Saint Gregory of Tours was a Gallo-Roman historian and Bishop of Tours, which made him a leading prelate of Gaul. He was born Georgius Florentius, later adding the name Gregorius in honour of his maternal great-grandfather...

 mentions Illidius in his work.
The fountain of St. Allyre at Clermont is known for its petrifying water, caused by calcareous

Calcareous

Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...

deposits.