Roselite

Formula: Ca₂(Co,Mg)(AsO₄)₂.2H₂O

Origin of name: for Gustav Rose, German mineralogist

Crystal system: monoclinic

Crystal class: 2/m

Twinning: common on {100}, often fourlings

Unit cell: a = 5.80 Å, b = 12.90 Å, c = 5.62 Å, b = 107.4°

Colour: dark rose-red to pink

Diaphaneity: 

Luster: vitreous

Habit: crystals short prismatic or thick tabular, as druses or spherical aggregates

Hardness: 3.5

Specific gravity: 3.69

Cleavage: 1; {010} perfect, easy

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: series with wendwilsonite, dimorphous with beta-roselite