Winchite

Formula: [](CaNa)(Mg,Fe)₄(Al,Fe)(SI,Al)₈O₂₂(OH)₂

Origin of name: for Howard J. Winch, British geologist, Geological Survey of India, who discovered the mineral

Crystal system: Monoclinic

Crystal class: 2/m

Twinning:

Unit cell: a = 9.83, b = 18.062, c = 5.3, β = 104.4°

Colour: Cobalt blue to bluish violet, lavender gray, gray

Diaphaneity: Translucent to subopaque

Luster: Vitreous

Habit: Crystals prismatic, acicular, fibrous or bladed, in rosettes

Hardness: 5 to 6

Specific gravity: 2.97

Cleavage: 2; {110} and {1-10}good, intersecting at ~56° and ~124°, partings on {100} and {001}

Tenacity: Brittle, uneven fracture

Streak: Bluish white

Synonyms/varieties:

Comments: series with ferrowinchite