Mineral Information and Data:

Barytolamprophyllite
Na3(BaK)Ti3(Si2O7)2O2(OH)2 [CNMNC approved formula]

Named for the composition - Barium and similarity to lamprophyllite.

IMA status : Approved Species 1965 ()
CLASSIFICATION 
Dana
(8th edition) :
56.02.06c.01  
  (56) Sorosilicate Si2O7 Groups and O, OH, F. and H2O
  (56.02) with cations in [4] and/or >[4] coordination
  (56.02.06c) Seidozerite - Lamprophyllite group (Lamprophyllite subgroup)
  
Nickel-Strunz
(10th edition) :
09.BE.25
  (09) Silicates
  (09.B) Sorosilicates (dimer) structures
  (09.BE) Si2O7 groups, with additional anions; cations in octahedral [6] and greater coordination
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: C2/m
Unit cell: a = 19.83Å, b = 7.08Å, c = 5.39Å; β = 96.66°
Crystal Habit: As foliated aggregates of cleavable pseudorhombohedra.
  
Color: Dark brown
Diaphaneity: Semitransparent
Luster: Vitreous
Hardness (Mohs): 2 - 3
Measured Density: 3.62 - 3.66 g/cm3
Cleavage: Perfect on {100}, less so on {011}, imperfect on {010}
Tenacity: Brittle
  
Geologic Setting: In ijolite (Lovozero massif, Russia).
Mineral Association: Aegirine, nepheline, potassic feldspar, cancrinite, apatite (Lovozero massif, Russia); amphibole, eudialyte, natrolite, pectolite (Gardiner complex, Greenland).
  

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