Ransomite

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]

Ransomite
General
Category	Sulfate
Formula	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	[1][2][3]

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]