The open encyclopedia of minerals
GlossaryCite the database
Mineralogist.org
Minerals A–ZSearchCollectionsBrowse by PropertyIdentify a SpecimenCompare MineralsLocalities MapGlossaryContribute Search the Database →
Phosphate

Mejillonesite

NaMg₂(PO₃OH)(PO₄)(OH)·H₅O₂
Hardness4
Crystal systemOrthorhombic
ClassPhosphate
←PrevMeixneriteNextMelanarsite→
Mejillonesite specimen

Mejillonesite Locality: Cerro Mejillones, Mejillones peninsula, Mejillones , Antofagasta Province, Antofagasta Region, Chile Original description: splendid group of colourless crystals of Mejillonesite. Dimension area 1,9 x 1,9 mm photo Germano Fretti, collection Luigi Chiappino — Photo: Germano Fretti (uploaded on mindat.org by Luigi Chiappino · CC BY-SA 3.0

Mejillonesite

Mejillonesite is an IMA-recognized mineral species in the phosphate class, with the chemical formula NaMg₂(PO₃OH)(PO₄)(OH)·H₅O₂.

It crystallizes in the orthorhombic crystal system (space group Pbca).

Key properties: Mohs hardness 4; specific gravity 2.36; White streak; Vitreous luster; optically biaxial.

IMA symbol Mej, IMA status: approved, named in 2010.

Formed at the contact between granite and what is now a fine-grained, completely altered siliceous layer at the base of a Pliocene (ca. 2.5 Ma) coastal bird guano deposit.

It is found associated with Bobierrite, opal, clinoptilolite-Na, clinoptilolite-K, gypsum.

The name is derived from the locality that provided the first specimen.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more M minerals or help write this entry.