Mineral Information and Data:

Na9(Si27Al9)O72 • 28H2O [CNMNC approved formula]

Named as the sodium-dominant phase of the stilbite series. Species named from the Greek stilbe - "luster" in allusion to its pearly to vitreous luster. Name and defined per nomenclature for zeolite minerals (IMA, 1997).

IMA status : Approved Species 1997 ()
(8th edition) :  (This Dana# Added)
  (77) Tectosilicate Zeolite group
  (77.01) true zeolites
  (77.01.04) Heulandite and related species
(10th edition) :
  (09) Silicates
  (09.G) Tektosilicates with Zeolitic H2O
  (09.GE) Chains of T10O20 Tetrahedra
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: P2/m
Unit cell: a = 13.63Å, b = 18.17Å, c = 11.31Å
Crystal Habit: Crystals typically thin tabular, flattened on [010], to 14 cm; in fasicled, sheaf-like, or globular aggregates
Twinning: Universal on {001} penetration, cruciform
Color: White, yellowish, gray, pink, reddish, orange, light brown to dark brown
Diaphaneity: Transparent, Translucent
Luster: Vitreous, pearly on cleavage
Hardness (Mohs): 3.5 to 4
Measured Density: 2.1 - 2.2 g/cm3
Cleavage: 2; {010} perfect, {100} distinct
Tenacity: Brittle
Fracture: Uneven
Streak: White
Geologic Setting: A low-temperature hydrothermal mineral, in amygdules and cavities in basalts, andesites, and various metamorphic rocks. Formed in hot springs deposits, and as a cementing agent in some sandstones and conglomerates.
Mineral Association: Zeolites, prehnite, calcite, quartz


White stilbite-Na on matrix.
Origin: Cape Pula, Pula, Cagliari Province, Sardinia, Italy.
Photo: Ed Rosenzweig