Gobbinsite |(Na, Ca0.5)6 (H2O)12| [Al6Si10O32]
       
Morphology:    
  Compact masses up to 2 cm, consisting of finely fibrous crystals, or wedge-shaped crystals.

gobbinsiteGobbinsite crystals from Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada

  
   
Physical properties:  
  Cleavage: none.
Fracture: brittle uneven.
Hardness:  4.5 - 5.
Density = 2.13 - 2.17 gm/cm3.
Luster: vitreous.
Streak: white.		  
   
Optical properties:            
  Color: Chalky white to light brown; colorless in thin section.
Uniaxial (-) or biaxial.  ω  1.494,  ε  1.489,  δ  0.005		  
   
Crystallography:  
  Unit cell data:
a  10.1035,  b  9.7819  c  10.1523 Å
Z = 1, Space group Pmnb    (Gatta et al. 2010)		  
   
   
       
Name:  
  Gobbinsite was named by Nawaz and Malone (1982) for the type locality, which is in basalt cliffs near Hills Port, south of the Gobbins area, County Antrim, Northern Ireland.
       
Crystal structure:  
  The gobbinsite has the same framework topology as gismondine, which consists of two sets of intersecting, doubly connected 4-membered rings linked into double crankshaft chains (dcc on the GIS page). These sets of double crankshaft chains that run parallel to the a-axis and the b-axis are related by a pseudo-41 axis parallel to the c-axis. Gobbinsite is the natural counterpart of the synthetic zeolite Na-P2 (Hansen et al. 1990). The structure of gobbinsite is equivalent to garronite-Na (Skrzynska et al. 2023).
  Because most gobbinsite occurs in masses of fibrous crystals so thin, none have been suitable for single crystal X-ray analysis. The structure of material was refined by the Rietveld technique by McCusker et al. (1985) and Artioli and Foy (1994) in the space group Pmn21. Gatta et al. (2010) refined the structure of crystals from near Victoria, Australia, by single crystal X-ray diffraction in the space group Pmnb.  The framework is highly disordered. In the channels parallel to the a-axis Na (yellow) is coordinated with four framework oxygens and two H2O molecules and Ca (orange is coordinated with five framework oxygens and two H2O molecules. Low-T study shows a significant rearrangement of the extra-framework configuration of gobbinsite (Gatta and Lotti 2011). Partial ordering of H2O and onset of new deformational modes occur at high-P (Gatta et al. 2012). gobbinsite
   
Chemical composition:
  In the few known gobbinsite samples that have been analyzed, the cation content is somewhat variable, but Na greatly predominates with Ca less than 0.6 atoms per unit cell. High K contents (greater than 0.1 atom per unit cell) is likely to be from intergrown phillipsite. All four analyzed gobbinsite samples have 10.4 Si or less per unit cell. The H2O content is likely to be approximately 17 weight per cent, which corresponds to 12 H2O molecules per unit cell (Deer et al. 2004, and Gatta et al. 2010).
   
Occurrences:
  The type specimen was found in basalt cavities on Island Magee, Northern Ireland (Nawaz and Malone 1982). Walker (1962) suggests sea water in place of the usual meteoric water was responsible for the crystallization of the sodic zeolites or may have caused later alteration of garronite to gobbinsite. Gobbinsite occurs as fibrous crystals in amygdules of altered trachybasalt at Kuniga, Dozen, Oki Islands, Shimane Prefecture, Japan (Matsuyama and Matsubara 2000), where it is associated with cowlesite and levyne. It occurs as glassy, wedge-shaped crystals in a basalt quarry (Boral Quarry) at Bundoora, a northern suburb of Melbourne, Victoria, Australia, associated with chabazite-Na, phillipsite-Na, gonnardite, natrolite, and thomsonite-Ca (Gatta et al. 2010).

Gobbinsite has also been found in a eudialyte pegmatitic lens in the nepheline syenite, exposed in the Poudrette Quarry, Mont Saint-Hilaire, Quebec (Horvath and Gault 1990).
   
References:
  Artioli, G. and Foy, H. (1994) Gobbinsite from Magheramorne quarry, Northern Ireland. Mineral. Mag. 58, 615-620.

Deer, A., Howie, R., Wise, W.S., and Zussman, J. (2004) Rock Forming Minerals. vol. 4B.  Framework Silicates: Silica Minerals, Feldspathoids and the Zeolites. The Geological Society, London.

Gatta, G.D., Birch, W.D., Rotiroti, N. (2010) Reinvestigation of the crystal structure of the zeolite gobbinsite: A single-crystal X-ray diffraction study. Am. Mineral. 95, 481-486.

Gatta, G.D. and Lotti, P. (2011) On the low-temperature behavior of the zeolite gobbinsite: A single-crystal X-ray diffraction study. Microporous mesoporous mater., 143(2-3), 467-476.

Gatta, G.D., Lotti, P., Nestola, F. and Pasqual, D., (2012) On the high-pressure behavior of gobbinsite, the natural counterpart of the synthetic zeolite Na–P2. Microporous Mesoporous Mater., 163, 259-269.

Hansen, S., Håkansson, U. and Fälth, L. (1990) Structure of synthetic zeolite Na-P2. Acta Cryst. C, 46(8), 1361-1362.
Horvath, L and Gault, R.A. (1990) The mineralogy of Mont Saint-Hilaire Quebec. Mineral. Record. 21, 284-359.

Matsuyama, F. and Matsubara, S. (2000) Gobbinsite from Kuniga, Dozen, Oki Islands, Shimane Prefecture, Japan. Japan. Mag. Mineral. Petrol. Sci. 29, 129-135.

McCusker, L.B., Baerlocher, C. and Nawaz, R. (1985) Rietveld refinement of the crystal structure of the new zeolite mineral gobbinsite. Z. Kristallogr. 115, 439-450.

Nawaz, R. and Malone, J.F. (1982) Gobbinsite, a new zeolite mineral from Co. Antrim, N. Ireland. Mineral. Mag. 46, 365-369.

Skrzynska, K., Cametti, G., Juroszek, R., Schafer, C. and Galuskina, I. (2023) New data on minerals with the GIS framework-type structure: gismondine-Sr from the Bellerberg volcano, Germany, and amicite and Ba-rich gismondine from the Hatrurim Complex, Israel. Mineral. Mag., 87(3), 443-454.

Walker, G.P.L. (1962) Garronite, a new zeolite, from Ireland and Iceland. Mineral. Mag. 33, 173-186.

Updated: June 2025.