Umbozerite

Formula: Na₃Sr₄ThSi₈(O,OH)₂₄

Origin of name: after locality Lake Umbozero, Kola Peninsula, Russia

Crystal system: Metamict (amorphous due to radiation damage), tetragonal after recrystallisation

Crystal class: -

Twinning:

Unit cell: -

Colour: Bottle-green to mottled greenish brown

Diaphaneity: Translucent to transparent

Luster: Vitreous

Habit: Metamict, pseudo-tetragonal, poorly formed, to 3 mm, irregular masses

Hardness: 5

Specific gravity: 3.60

Cleavage: None

Tenacity: Brittle, conchoidal fracture

Streak: 

Synonyms/varieties:

Comments:  Radioactive