Stronadelphite
Stronadelphite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Sr₅(PO₄)₃F.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Apatite structural group.
Key properties: Mohs hardness 5; specific gravity 3.915; White streak; Vitreous luster; optically uniaxial.
IMA symbol Sad, IMA status: approved, named in 2008.
From hydrothermal alteration of peralkaline pegmatite is a sinuous and branched vein cross-cutting inequigranular nepheline syenite in an alkaline massif.
It is found associated with Natrolite, microcline, aegirine, pectolite, lamprophyllite, belovite-(Ce), belovite-(La), gaidonnayite, nenadkevichite, komarovite, manganokukisvumite.
The name commemorates the chemical element strontium and adelfós, Greek for ‘‘brother’’, as the full strontium analogue of fluorapatite, the most widespread member of the apatite supergroup.