Formula: (Ce,La)2Al(SiO4)2(OH)
Origin of name: for Alfred Ellis Törnebohm (1839-1911), former director of the Geological Survey of Sweden
Crystal system: Monoclinic, pseudohexagonal
Crystal class: 2/m
Twinning:
Unit cell: a = 7.383, b = 5.673, c = 16.937, β = 112.04°
Colour: Olive-green to green (Ce), dark green or greenish gray (La)
Diaphaneity: Semitransparent
Luster: Vitreous to adamantine
Habit: massive, fine grained, as inclusions in cerite
Hardness: 4.5
Specific gravity: 4.90-4.94
Cleavage:
Tenacity:
Streak:
Synonyms/varieties:
Comments: Two distinct species with the extensions -(Ce) and -(La) indicating the predominant rare earth element in the formula. Found in rare-earth ore deposits.
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