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Pyrrhotite (Photo) [abbr. Po ]

Year of discovery: 1847 (World), 1875 (Japan)

Locality list: 1,328 localities of pyrrhotite

• Fe₇S₈
• Fe_(1-x)S
• [Fe²⁺₇][S₈]
• x=0-0.17

• Class: Sulfide
• Soluble in: HCl (Decompose)
• Magnetism: Paramagnetic, Ferrimagnetic (Strength variable)
• Alter to Römerite (Romerite).

• x=0: Troilite (Non-magnetic)

• Fe => (Fe,Ni): Smythite

• Color: Yellowish brown
• Tarnish: Dark brown
• Streak: Grayish black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Hexagonal platy on {0001}, Prismatic, Pyramidal
• Aggregate: Rosette nearly parallel on {0001}
• Twin: {10-12}

• Cleavage: No, Parting on {0001} (1 plane)
• Hardness: 3.5-4
• Density: 4.6

• System: Monoclinic (4M, Fe₇S₈), Monoclinic (6M, Fe₁₁S₁₂), Hexagonal (5H, Fe₉S₁₀), Hexagonal (7H, Fe₉S₁₀), Hexagonal (11H, Fe₁₀S₁₁), Cubic (5C) (Layer-stacking polytype)
• Group: 2/m, A2/a
• Lattice: a=11.9, b=6.9, c=22.8, β=90.5

• Significance (Contact meta.): High temperature (more than 325 degree) and Reductive condition. Pyrite is stable below 325 degree.

Etymology: Pyrroh (Red color) in Greek.