Agrellite

Formula:  NaCa₂Si₄O₁₀F

Origin of name:  for Stuart Agrell, English mineralogist

Crystal system:  Triclinic

Crystal class:  -1

Twinning:

Unit cell: a = 7.759 Å, b = 18.946 Å, c = 6.986 Å, a = 89.88°, b = 116.65°, g = 94.32°

Colour:  White to grayish or greenish white

Diaphaneity: Transparent to translucent

Luster: Vitreous, pearly on cleavage

Habit:  Crystals elongated and flattened

Hardness:  5.5

Specific gravity:  2.90

Cleavage:  3; on {110}, {1-10} excellent, on {010} poor

Tenacity:

Streak: White

Synonyms/varieties:

Comments:  Fluoresces bright pink under long wavelength UV and duller pink under short wavelength UV. Found in pegmatite lenses and pods and in mafic gneisses in a regionally metamorphosed agpaitic alkalic rock complex