Formula: Na2AlSi3O8(OH)
Origin of name: for Niels Viggo Ussing (1864-1911), Danish mineralogist, Copenhagen
Crystal system: Triclinic
Crystal class: 1
Twinning: Common on {010}
Unit cell: a = 7.256, b = 7.686, c = 8.683, α = 90.75°, β = 99.75°, γ = 122.48°
Colour: White, reddish violet, lighr violet red, dark violet red, lilac blue, may be tarnished on the surface
Diaphaneity: Transparent
Luster: Slightly greasy to vitreous, slightly pearly on cleavage
Habit: Massive, rarely as pseudocubic to tabular crystals to 1 cm, finegrained, compact
Hardness: 6.5
Specific gravity: 2.46 to 2.5
Cleavage: 2; {110} and {110} perfect
Tenacity: Brittle, uneven fracture
Streak: White
Synonyms/varieties:
Comments:
| Back to Alphabetical list | Colour photos | Optical properties/Thin sections | SEM images | TEM images | vibrational spectra description | IR spectra | Raman spectra | N-IR spectra | F-IR spectra | IES spectra |