Ransomite

Ransomite
Ransomite
General
Category	Sulfate
Formula; (repeating unit)	CuFe2(SO4)4*6H2O
Crystal system	Monoclinic
Crystal class	2/m - Prismatic
Space group	P21/b
Unit cell	a = 4.811 Å, b = 16.217 Å ; c = 10.403 Å; ; β= 93.01°; Z = 2
Identification
Formula mass	667.59
Color	Bright sky blue; pale blue in transmitted light
Crystal habit	needle-like crystals
Cleavage	Perfect along {010}
Tenacity	Radiating tufts and crusts
Mohs scale hardness	2.5
Luster	Vitreous, pearly cleavage
Diaphaneity	Transparent
Density	2.632 g/cm3
Optical properties	Biaxial positive
Refractive index	nα= 1.631 nβ= 1.643 nγ= 1.695
Birefringence	δ = 0.064
Dispersion	v > r strong
References

Ransomite is a sulfate mineral first discovered at the United Verde mine in Jerome Arizona. This mineral was formed as a result of a mine fire. The United Verde mine is one of few places in the world where Ransomite can be found. This mineral can be described as a soluble sulfate that forms needle-like crystals and has a pale blue color in transmitted light.^[1] This mineral was named by Carl B. Lausen as a tribute to Frederick Leslie Ransome. Ransome was an American mining geologist who worked at the California Institute of Technology, the University of Arizona and the United states Geological Survey.^[2]

Occurrence

Ransomite is found in association with pyrite, voltaite, and romerite. These minerals can be found in Campbell shaft, Arizona.^[3] Ransomite tends to form in the cavities of crushed up rock in these different mines. In these cavities, Ransomite forms small radiating crystals and pale-blue crusts.^[1]

Physical properties

Ransomite is a bright sky blue or a pale blue in transmitted light, transparent mineral with a vitreous, pearly luster. It exhibits a hardness of 2.5 on the Mohs hardness scale.^[2] Ransomite occurs as needle-like crystals and has radiating tufts and crusts. Ransomite has perfect cleavage along the {010} plane. The specific gravity is 2.632 g/cm³.^[2]

Optical properties

Ransomite is biaxial positive, this means it can refract light on two axes. The refractive indices are: α ~ 1.631, β ~ 1.643, and γ ~ 1.695 (Na). Dispersion is strong, v > r. Ransomite has a max birefringence of 0.064 and has a moderate surface releif. ^[2]

Chemical properties

Ransomite is a sulfate that has a similar formula to the mineral Cuprocopiapite. Cuprocopiapite has a specific gravity of (2.23 g cm₋₃), which is close to the value of Ransomite. ^[2]

Chemical composition

Oxide	wt%
SO₃	46.30
Al₃O₃	1.52
Fe₂O₃	22.57
CuO	11.29
H₂O	18.82
Total	100.50

^[3]

X-ray crystallography

Ransomite is in the monoclinic crystal system. The space group associated with Ransomite is P2₁/b with unit cell dimensions: a = 4.811Å, b = 16.217Å, c = 10.403Å; β= 93.01°; Z=2. Ransomite has a point group of 2/m and is prismatic. It also has skinny prisms extended parallel to the c axis. ^[2]

References

^ ^a ^b ^c Wood, M.M., 1970, The Crystal Structure of Ransomite, The American Mineralogist, v. 55, p.729-734
^ ^a ^b ^c ^d ^e ^f ^g Hudson Institute of Mineralogy, 2023, Ransomite: https://www.mindat.org/min-3364.html (accessed November 2023)
^ ^a ^b ^c Mineral Data publishing, 2001-2005, Ransomite: https://www.handbookofmineralogy.org/pdfs/ransomite.pdf (accessed November 2023)

[Wood-1] Wood, M.M., 1970, The Crystal Structure of Ransomite, The American Mineralogist, v. 55, p.729-734

[mindat-2] ^ ^a ^b ^c ^d ^e ^f ^g Hudson Institute of Mineralogy, 2023, Ransomite: https://www.mindat.org/min-3364.html (accessed November 2023)

[handbookofmineralogy-3] Mineral Data publishing, 2001-2005, Ransomite: https://www.handbookofmineralogy.org/pdfs/ransomite.pdf (accessed November 2023)

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