Mineral Information and Data:

Gmelinite-K
K4(Si8Al4)O24 • 11H2O [CNMNC approved formula]

Named as the potassium-dominant phase of the gmelinite series. Species named for Christian Gottlob Gmelin (1792-1860), German mineralogist and chemist, from Turbingen, Germany. Named per nomenclature for zeolite minerals (IMA, 1997).

IMA status : Approved Species 2001 (IMA1999-039)
CLASSIFICATION 
Dana
(8th edition) :
77.01.02.06b  (This Dana# Added)
  (77) Tectosilicate Zeolite group
  (77.01) true zeolites
  (77.01.02) Chabazite and related species
  
Nickel-Strunz
(10th edition) :
09.GD.05
  (09) Silicates
  (09.G) Tektosilicates with Zeolitic H2O
  (09.GD) Chains of 6-membered rings - tabular zeolites
  
Crystal system: Hexagonal System
Point group (H-M): 6/mmm (or 6/m 2/m 2/m) — dihexagonal-dipyramidal
Space group: Р63/mmc
Unit cell: a = 13.696(2)Å, c =10.203(2)Å, Z = 1
Crystal Habit: соlumпаг ог acilular crystals elongated along [001]
  
Color: Colorless ог brownish
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 4
Measured Density: 2.00 g/cm3
Tenacity: Brittle
Fracture: Conchoidal
Streak: White
  
Geologic Setting: In drusy aggregates in cavities of brecciated pegmatoids.
  
Other Properties: Gemstone Extremely Rare.

 

Gmelinite-K
Pink to reddish brown gmelinite-K crystals in cavity in matrix
Origin: Fara Vicentino, Vicenza, Veneto, Italy
Sample size: micromount
Photo: Diederik Visser

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