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)
