Formula: (Al,Mg,Fe,Ti)22(O,OH)32
Origin of name: after Arvid Gustaf Hogbom (1857-1940), Swedish geologist, University of Uppsala and composition/crystal structure (S = spinel, N = nolanite layers)
Crystal system: Hexagonl
Crystal class: 6mm
Twinning:
Unit cell: a = 5.734 Å, c = 18.389 Å
Colour: Black
Diaphaneity: Subtranslucent to opaque
Luster: Adamantine
Habit: Tabular, thin in one direction
Hardness: 6.5
Specific gravity: 3.81 (4.02 calculated)
Cleavage: [0001] imperfect
Tenacity: conchoidal fracture
Streak: Gray
Synonyms/varieties: hoegbomite, hogbomite-8A
Comments:
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