Edingtonite

Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl₂Si₃O₁₀·4H₂O. It has varieties with tetragonal, orthorhombic or triclinic crystals.^[5]

Edingtonite
Edingtonite from Ice River Alkaline Complex, Golden Mining Division, British Columbia, Canada
General
Category	Tectosilicate minerals, zeolite group
Formula	BaAl2Si3O10·4H2O
IMA symbol	Edi[1]
Strunz classification	9.GA.15
Crystal system	Orthorhombic
Identification
Color	White, gray, pink
Crystal habit	Prismatic pseudotetragonal crystals; massive.
Twinning	On [110] and [001]
Cleavage	Perfect on [110]
Mohs scale hardness	4 - 4.5
Specific gravity	2.73 - 2.78
Optical properties	Biaxial (-)
Refractive index	nα = 1.538 nβ = 1.549 nγ = 1.554
Birefringence	δ = 0.016
2V angle	54 - 62°
Dispersion	r < v; strong
Other characteristics	Pyroelectric and piezoelectric
References	[2][3][4]

The mineral occurs within cavities in nepheline syenites, carbonatites, in hydrothermal veins and various mafic rocks. It occurs associated with thomsonite, analcime, natrolite, harmotome, brewsterite, prehnite and calcite.^[4]

The mineral was first reported by and named for Scottish mineral collector James Edington (1787–1844).^[3][4] Other sources (including the mineralogist Haidinger) credit Scottish geologist and mineralogist Thomas Edington (1814-1859).^[6] However, as the mineral was named in 1825, the former accreditation must be the true one.^[7]