Goslarite

Goslarite is a hydrated zinc sulfate mineral (ZnSO₄ · 7 H₂O) which was first found in the Rammelsberg mine, Goslar, Harz, Germany. It was described in 1847. Goslarite belongs to the epsomite group which also includes epsomite (MgSO₄ · 7 H₂O) and morenosite (NiSO₄ · 7 H₂O). Goslarite is an unstable mineral at the surface and will dehydrate to other minerals like bianchite (ZnSO₄ · 6 H₂O), boyleite (ZnSO₄ · 4 H₂O) and gunningite (ZnSO₄ · H₂O).

Goslarite
Goslarite on display at the Museo Nacional de Ciencias Naturales
General
Category	Sulfate mineral
Formula	ZnSO4·7H2O
IMA symbol	Gos[1]
Strunz classification	7.CB.40
Crystal system	Orthorhombic
Crystal class	Disphenoidal (222) (same H-M symbol)
Space group	P212121
Unit cell	a = 11.8176 Å, b = 12.0755 Å c = 6.827 Å, Z = 4
Identification
Formula mass	287.56 g/mol
Color	Colorless, pinkish, white, greenish, green, blue, green blue, bluish and brownish
Crystal habit	Acicular, massive, stalactitic
Cleavage	{010} perfect
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	2.0–2.5
Luster	Vitreous (glassy)
Streak	White
Specific gravity	1.96
Optical properties	Biaxial (-)
Refractive index	nα = 1.447 - 1.463 nβ = 1.475 - 1.480 nγ = 1.470 - 1.485
Birefringence	δ = 0.0220–0.0230
Pleochroism	none
2V angle	46°
References	[2][3][4][5]

Physical properties

The composition of goslarite was determined by the US National Bureau of Standards (now the National Institute of Standards and Technology) in 1959 as follows: SO₃ 27.84 wt%, ZnO 28.30 wt% and H₂O 43.86 wt%.

Goslarite's cleavage is perfect in {010}, as for epsomite and morenosite. The color of goslarite ranges from brownish to pinkish, blue, brown, colorless, green and green blue. The luster ranges from vitreous to nacreous and silky (if fibrous). Goslarite is soluble in water, has an astringent taste, and is strongly diamagnetic.^[6][7][8]

Geologic occurrence

Goslarite is formed from the oxidation of sphalerite ((Zn, Fe)S).^[9] It was first found in Rammelsberg mine, Goslar, Harz, Germany. It often occurs as an efflorescence on timbers and walls of mine passages. Goslarite is widespread as a post mining efflorescence in mines that contain sphalerite or any zinc minerals.

Economical uses

In the pharmaceutical industry it is used as a direct emetic, antiseptic and disinfectant.^[10]