Ashcroftine

Formula:  K₅Na₅(Y,Ca)₁₂Si₂₈O₇₀(OH)₂(CO₃)₈^.8H₂O

Origin of name:  For Frederick Noel Ascroft (1878-1949), British mineralogist, benefactor to the British Museum (Natural History), London, England

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 24.01 Å, c = 17.52 Å

Colour:  Pale pink, white, pinkish brown, deep violet-brown

Diaphaneity: Transparent to translucent

Luster:  Vitreous, sometimes silky

Habit:  Crystals fibrous prismatic, powdery, crystals striated

Hardness:  5

Specific gravity:  2.61

Cleavage:  2; {100} perfect, {001} distinct

Tenacity: Flexible

Streak: White

Synonyms/varieties:

Comments: Found in cavities in augite syenite; in igneous breccia and pegmatites in an intrusive alkalic gabbro-syenite complex