Compact nodule of this rare iron phosphate. Brilliant, with visible conchoid fracture. With yellow earthy jarosite-limonite. Bruguers area is well know for rare phosphate species. Collected: 03/2017 (Cal Gairal street outcrops, Bruguers, Gavà, Baix Llobregat, Barcelona, Catalonia). Outcrop in a construction works, nowadays desapeared under building. — Photo: Joan Rosell , from rosellminerals.com · CC BY 4.0
Delvauxite
An amorphous yellow-to-brown hydrated iron-calcium phosphate-sulfate forming botryoidal masses — also called borickite.
Intro adapted from Wikipedia (CC BY-SA).
Delvauxite is an IMA-recognized mineral species in the phosphate class, with the chemical formula CaFe³⁺₄(PO₄)₂(OH)₈·4-5H₂O.
It crystallizes in the amorphous crystal system. It is a member of the Amorphous structural group.
Key properties: Mohs hardness 3.5; specific gravity 2.38–2.53; Pale brown streak; Waxy to opaline luster.
IMA symbol Dvx, IMA status: questionable, named in 1838.
Found in gossan (Nenačovice, Czech Republic).
It is found associated with Diadochite, vivianite, pitticite, melanterite, “limonite”.
In honor of J.S.P.J. Delvaux de Feuffe (1782–1863), Belgian chemist, who first analyzed the mineral.