Bílinite

Bílinite (Fe²⁺Fe₂³⁺(SO₄)₄·22H₂O) is an iron sulfate mineral. It is a product of the oxidation of pyrite in water. It is an acidic mineral that has a pH of less than 3 and is harmful to the environment when it comes from acid rock drainage (Keith et al., 2001).

Bílinite
General
Category	Sulfate mineral
Formula	Fe2+Fe3+2(SO4)4·22H2O
IMA symbol	Bli[1]
Strunz classification	7.CB.85
Dana classification	29.07.03.05
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/c
Identification
Color	White to yellowish
Crystal habit	Fibrous in radial aggregates
Mohs scale hardness	2
Luster	Vitreous - silky
Streak	White
Diaphaneity	Semitransparent
Specific gravity	1.87
Optical properties	Biaxial (+/-)
Refractive index	nα = 1.480 - 1.482 nβ = 1.500 nγ = 1.489 - 1.493
Birefringence	δ = 0.009 - 0.011
Solubility	Soluble in water
References	[2][3][4]

Bílinite was first discovered near Bílina, Czech Republic which is why the mineral was named 'bílinite' (Palache, et al., 1969). This mineral possibly occurs on Mars.

Composition

The weight percent oxide is as follows:^[2]

Oxide	Composition
SO3	33.78
Fe2O3	16.84
FeO	7.58
H2O	41.8
Total	100

Related minerals

Related minerals to bílinite include jarosite, which is an iron sulfate salt, lepidocrocite, schwertmannite, ferricopiapite, and copiapite (Marion, et al., 2008).

Special characteristics

Boulder Creek is a stream at Iron Mountain in Shasta County, California. The stream drains into the Sacramento River and San Francisco Bay. The water in this stream is contaminated from the mixture of the groundwater and surface streams due to mining. The pH is low and acidic due to the oxidation of pyrite in water. This results in the formation of sulfuric acid and bílinite (Keith, et al., 2001).