Arrojadite

Formula:  KNa₂CaMn₄Fe₁₀Al(PO₄)₁₂(OH,F)₂

Origin of name:  For Miguel Arrojada Ribeiro Lisbôa (1872-1932), Brazilian geologist

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 24.692 Å, b = 10.031 Å, c = 16.453 Å, b = 105.72°

Colour:  Dark green to yellowish green, clove brown

Diaphaneity: Translucent

Luster:  Vitreous to greasy

Habit:  Crystals well-formed; cleavable masses

Hardness:  5

Specific gravity:  3.53

Cleavage:  2; {100} good, {102} poor

Tenacity:

Streak: Green gray

Synonyms/varieties:

Comments:  Series with dickinsonite. A high-temperature (about 800°C) primary mineral in granite pegmatites.