Mineral Information and Data:

BaBe2Si2O7 [CNMNC approved formula]

Named from the Greek for "heavy", in allusion to its high specific gravity.

IMA status : Valid species (Pre-IMA 1876) Grandfathered
(8th edition) :  
  (55) Sorosilicate Si2O7 Groups, Generally with No Additional Anions
  (55.01) with cations in [4] and higher coordination
(10th edition) :
  (09) Silicates
  (09.B) Sorosilicates (dimer) structures
  (09.BB) Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination
Crystal system: Orthorhombic System
Point group (H-M): mm2 — pyramidal
Space group: Pn21a
Unit cell: a = 9.82Å, b = 11.67Å, c = 4.69Å
Crystal Habit: As thin tabular to prismatic crystals displaying square cross sections, to 2 cm; granular, massive.
Color: Colorless, white, blue
Diaphaneity: Translucent
Luster: Vitreous to greasy
Hardness (Mohs): 7
Measured Density: 4.066(2) g/cm3
Cleavage: Good on {001} and {100}, imperfect on {010}.
Tenacity: Brittle
Geologic Setting: In a banded vein in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA); in an "amazonite" pocket (Park Co., Colorado, USA); in narrow veins in chertlike silica and albite in fenitized gneisses (Seal Lake, Canada); in calcite veins cutting amphibole gneisses (Vishnevye Mountains, Russia).
Mineral Association: Hedyphane (Langban, Sweden); hedyphane, willemite (Franklin, New Jersey, USA); microcline, barite, fluorite (Park Co., Colorado, USA); eudialyte (Seal Lake, Canada); bastnasite, aeschynite, barite, strontianite, thorogummite, harmotome, fluorite, quartz (Vishnevye Mountains, Russia)
Luminescent Properties: May fluoresce vivid blue.