Rozenite

Rozenite is a hydrous iron sulfate mineral, Fe²⁺SO₄•4(H₂O).

Rozenite
Rozenite from Morocco
General
Category	Sulfate mineral
Formula (repeating unit)	Fe2+SO4•4(H2O)
IMA symbol	Rzn[1]
Strunz classification	7.CB.15
Dana classification	29.06.06.01
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/n
Identification
Color	Colorless, white, pale green
Crystal habit	As concretions and nodules; most commonly as powdery efflorescences or coatings on melanterite
Mohs scale hardness	2 - 3
Luster	Vitreous to dull
Streak	White
Diaphaneity	Semitransparent
Specific gravity	2.29
Optical properties	Biaxial (-)
Refractive index	nα = 1.526 - 1.528 nβ = 1.536 - 1.537 nγ = 1.541 - 1.545
Solubility	Water soluble
References	[2][3][4]

It occurs as a secondary mineral, formed under low humidity at less than 21 °C (70 °F) as an alteration of copper-free melanterite, which is a post mine alteration product of pyrite or marcasite. It also occurs in lacustrine sediments and coal seams. Associated minerals include melanterite, epsomite, jarosite, gypsum, sulfur, pyrite, marcasite and limonite.[2]

It was first described in 1960 for an occurrence on Ornak Mountain, Western Tatra Mountains, Małopolskie, Poland. It was named for Polish mineralogist Zygmunt Rozen (1874–1936).[2][3]

The thermal expansion of rozenite was studied from −254 °C (−425.2 °F) to 17 °C (63 °F) using neutron diffraction. Rozenite exhibits negative linear thermal expansion, meaning that it expands in one direction upon cooling.[5]