Delvauxite, also known as borickite, is a yellow to brown to dark brown amorphous mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

, sometimes forming a botryoidal

Botryoidal

A botryoidal texture or mineral habit is one in which the mineral has a globular external form resembling a bunch of grapes as derived from the Greek. This is a common form for many minerals particularly hematite where it is the classically recognized shape. It is also a common form of goethite,...

 mass. Its chemical formula is CaFe₄(PO₄,SO₄)₂(OH)₈•(4-6)H₂O. It may sometimes form stalactite

Stalactite

A stalactite , "to drip", and meaning "that which drips") is a type of speleothem that hangs from the ceiling of limestone caves. It is a type of dripstone...

s.

It was first described in 1838 by Belgian chemist, Dumont and dedicate to J.S.P.J. Delvaux de Feuffe (1782-1863). It was found in Bernau, Liege, Belgium

Belgium

Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

 and Stredocesky, Czech republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

.