Single isolated colorless crystal of the extremely rare mineral diaoyudaoite (Q3706785) from one of the few localities known worldwide. From: Port Elizabeth, Newark, Essex County, New Jersey, United States of America — Photo: David Hospital · CC BY-SA 4.0
Diaoyudaoite
Diaoyudaoite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula NaAl₁₁O₁₇.
It crystallizes in the hexagonal crystal system (space group P6_3/mmc). It is a member of the Magnetoplumbite structural group.
Key properties: Mohs hardness 7.6; specific gravity 3.3; optically uniaxial.
IMA symbol Dyd, IMA status: approved, named in 1985.
Found in the heavy-mineral (S.G. > 2.8) fraction of the surface layer of sea-floor muds at about 1500 m water depth.
It is found associated with Chromium inclusions; other heavy minerals include “hornblende”, epidote, dolomite, muscovite, chlorite, biotite.
The name refers to Diaoyudao Island, near which it occurs.