Walstromite

Formula: BaCa₂Si₃O₉

Origin of name: for Robert E. Walstrom (1920-), American mineral collector, who discovered the mineral.

Crystal system: Triclinic

Crystal class: 1

Twinning:

Unit cell: a = 6.723, b = 9.616, c = 6.733, α = 83.1°, β = 77.67°, γ = 69.62°

Colour: White to colourless

Diaphaneity: Transparent

Luster: Subvitreous, vitreous, pearly

Habit: Crystals short prismatic to nearly equant, anhedral to subhedral, from smaller than 1 mm up to 15 mm

Hardness: about 3.5

Specific gravity: 3.67

Cleavage: 3; {011}, {010} and {100} nearly perfect

Tenacity: 

Streak: White

Synonyms/varieties:

Comments: fluoresces dull pink under SW and bright pink to pinkish orange under LW ultraviolet light