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TABLE 1. Mineral names and chemical formulae referenced in this work. Molar volume is given per formula unit. Deliquescent minerals are marked “del.”

  Formula   Vol pfu (Å3)
Aluminum sulfates      
Halotrichite Fe2+Al2(SO4)4 • 22H2O del 791.3
Alunogen Al2(SO4)3 • 17H2O del 595.5
Ferrous sulfates      
Szomolnokite Fe2+SO4 • H2O   90.9
Rozenite Fe2+SO4 • 4H2O   785.5
Melanterite Fe2+SO4 • 7H2O del 243.9
Ferric sulfates      
Kornelite Fe23+(SO4)3 • 7H2O   387.5
Coquimbite Fe23+(SO4)3 • 9H2O (idealized) del 440.6
Coquimbite Fe2-x3+Alx(SO4)3 • 9H2O (actual) del 440.6
Quenstedtite Fe23+(SO4)3 • 10H2O   462.2
Fibroferrite Fe3+(SO4)(OH) • 5H2O   206.6
Rhomboclase HFe3+(SO4)2 • 4H2O   241.7
Mixed iron sulfates      
Römerite Fe2+Fe23+(SO4)4 • 14H2O   611.7
Jarosite (H3O),K,NaFe23+(SO4)2 (OH)6   264.9
Copiapite Fe2+Fe23+(SO4)6(OH)2 • 20H2O   1175.1
Sulfides      
Pyrite Fe2+S-2 (isometric)   39.8
Marcasite Fe2+S-2 (orthorhombic)   40.7
Pyrrhotite Fe(1-x)2+S (x = 0 to 0.2)   varies
Calcium sulfates      
Gypsum CaSO4 • 2H2O   123.8
Bassanite CaSO4 • 0.5 H2O   88.0
Anhydrite CaSO4   76.4
Iron oxides      
Hematite Fe2O3   50.5
Magnetite Fe3O4   74.0

 

 

TABLE 2. Stability of pyrite at elevated temperatures under a variety of atmospheres. DTA is differential thermal analysis, po is pyrrhotite, and py is pyrite. DTA peaks are the maxima of temperature for mineral transformation. Otherwise, the upper and lower brackets for the reactions are given.

Reference Atmosphere Results  
De Oliviera et al. (2019) N2 400°C py 600°C po appears
De Oliviera et al. (2019) CO2 400°C py 600°C po appears
Thomas et al. (2003) Argon 635°C py to po DTA  
Zhang et al. (2019) N2 in standard furnace 665°C DTA peak  
Zhang et al. (2019) N2 with microwave heating Po appears at 500°C  
Huang et al. (2015) CO2 560°C DTA peak  
Bhargava et al. (2009) 10-3 bar O2 400-850°C No po  
Bhargava et al. (2009) Air 400°C py 450°C hm, no py
Bhargava et al. (2009) Argon 500°C no po 600°C po appears
Bhargava et al. (2009) CO2 400°C no po 500°C po appears
Charpentier and Masset (2010) Argon+O2, 10-6 bar O 2 Po above 550°C DTA peak slightly above 600°C

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