Northupite

Northupite is an uncommon evaporite mineral, with the chemical formula Na₃Mg(CO₃)₂Cl. It occurs as colourless to dark grey or brown octahedral crystals and as globular masses. In synthetic material it forms a series with tychite (Na₆Mg₂(CO₃)₄SO₄).[3]

Northupite
Northupite octahedra
General
Category	Carbonate minerals
Formula (repeating unit)	Na3Mg(CO3)2Cl
IMA symbol	Nup[1]
Strunz classification	5.BF.05
Crystal system	Isometric
Crystal class	Diploidal (m3) H-M symbol: (2/m3)
Space group	Fd3
Unit cell	a = 13.98 Å; Z = 16
Identification
Colour	Colourless, pale yellow, grey, brown; colourless in transmitted light
Crystal habit	Octahedral crystals; globular, massive
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	3+1⁄2 - 4
Lustre	Vitreous
Diaphaneity	Transparent
Specific gravity	2.380–2.407
Optical properties	Isotropic
Refractive index	n = 1.5144 (to 1.550 with iron substitution)
Solubility	Readily soluble in dilute acids with effervescence. Decomposed by hot water with the separation of magnesium carbonate.
References	[2][3][4]

It was discovered in 1895 at Searles Lake, San Bernardino County, California by C. H. Northup (born 1861) from San Jose, California, for whom Northupite is named.

It occurs associated with tychite, pirssonite at Searles Lake and with shortite, trona, pirssonite, gaylussite, labuntsovite, searlesite, norsethite, loughlinite, pyrite and quartz in the Green River Formation of Wyoming.[2]