Stellerite

Stellerite is a rare mineral discovered by and named after Georg Wilhelm Steller, a German explorer and zoologist.[2] The mineral has a general formula of Ca[Al2Si7O18]·7H2O. Like most rare minerals, there are few commercial uses for stellerite. Mineral collectors are lucky to find it in good enough crystal form. Zeolites, including stellerite, have been studied using a dehydration process to gauge the potential use of their phases as molecular sieves, sorbents, and catalysts.[3]

Stellerite
General
CategoryZeolite mineral
Formula
(repeating unit)		Ca(Al2Si7O18)•7H20
IMA symbolSte[1]
Strunz classification9.GE.15
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupFmmm
Identification
ColorColorless to white, pink, orange
Crystal habitSpherical, Stellate, Tabular
CleavagePerfect on {010}
FractureUneven
Mohs scale hardness4.5
LusterPearly
Streakwhite
DiaphaneityTransparent to translucent
Specific gravityapproximately 2.2
Density2.13 g/cm3
Optical propertiesBiaxial (-), a=1.4848, b=1.4864-1.4964, g=1.4979
Birefringenceδ = 0.013
References[2]

Crystal habit

Stellerite is part of the orthorhombic crystal system which means it has three axes of unequal length that intersect at 90° angles. Its crystal class is rhombic-dipyramidal which means it has three perpendicular two-fold rotational axes with perpendicular mirror planes.[4] Stilbite, another zeolite, is very similar to stellerite in both chemical composition and physical appearance. Stellerite is more commonly found in rounded radiating clusters or as single crystals and appears more transparent than stilbite does.[4]

Optical properties

Stellerite is an anisotropic mineral, meaning that it has different properties in different directions-such as indices of refraction-when light passes through it. A refractive index (n) measures the speed of light in a substance—or in the case of mineralogy—in a mineral. It is expressed as a ratio of the speed of light in vacuum to that in a mineral.[5] Stellerite has three indices of refraction because it is a biaxial mineral.

Occurrence

Stellerite lines cavities and fracture surfaces in volcanic rocks altered by hydrothermal solutions. Great examples of Stellerite are on Copper Island, Commander Islands (also discovered by Georg Steller), Bering Sea and at Klichka, Chita region, Siberia, Russia. In the United States, it is located at Ritter Hot Springs, Grant County, Oregon; on Hook Mountain, Rockland County, New York; and at Fanwood, Union County, New Jersey. Large crystals have been found in Australia around Gunnedah, New South Wales, and at Harcourt, Dookie, and Corop, Victoria.[6]

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Pabst, Adolf (March 1939). "The relation of stellerite and epidesmine to stilbite". Mineralogical Magazine and Journal of the Mineralogical Society. 25 (164): 271–276. Bibcode:1939MinM...25..271P. doi:10.1180/minmag.1939.025.164.06.
  3. Arletti, R.; Mazzucato, E.; Vezzalini, G. (1 April 2006). "Influence of dehydration kinetics on T-O-T bridge breaking in zeolites with framework type STI: The case of stellerite". American Mineralogist. 91 (4): 628–634. Bibcode:2006AmMin..91..628A. doi:10.2138/am.2006.1966. hdl:2318/80204. S2CID 36048763.
  4. Miller, S. A.; Taylor, J. C. (1 January 1985). "Neutron single crystal diffraction study of an Australian Stellerite". Zeolites. 5 (1): 7–10. doi:10.1016/0144-2449(85)90003-X.
  5. "Index of Refraction." Encyclopedia Americana. Grolier Online http://ea.grolier.com/article?id=0213810-00 (accessed May 2, 2010)
  6. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Stellerite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 22 May 2022.
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