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Polydymite

Year of discovery: 1876 (Grüneau mine, Germany), 1940 (Japan)

Locality list: 10 localities of polydymite

• Ni₃S₄
• [Ni²⁺][Ni³⁺₂][S₄]^8-

• Class: Linnaeite subgroup < Thiospinel group < Spinel supergroup
• Class: Sulfide
• Soluble in: HNO₃ (Decompose)
• Insoluble in: HCl

• Ni => Co: Linnaeite (Series)
• Ni => Fe: Greigite
• Ni => Rh: Kingstonite

• Ni²⁺ => Cu: Fletcherite
• Ni²⁺ => Fe: Violarite (Series)
• Ni²⁺ => Co: Siegenite

• S => Se: Trüstedtite (Trustedtite)

• Color: Light gray, Dark gray
• Tarnish: Reddish brown-Purple
• Streak: Grayish black
• Luster: Metallic
• Diaphaneity: Opaque

• Habit: Octahedral
• Twin: {111}

• Cleavage: Imperfect on {001} (3 planes), also probably on {111}
• Hardness: 4.5-5.5
• Density: 4.6

• System: Cubic
• Group: m3m, Fd3m
• Lattice: a=9.5

Etymology: Poly (many) and Dym (twin) in Greek