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Berufjördur, Suður-Múlasýsla, Iceland
© Rob Lavinsky
|Colour:||White||Hardness:||3 - 3½|
|Name:||Named after the English mineral collector, John Henry Heuland (1778-1856), a British mineral collector and dealer|
|Heulandite-Ba, Heulandite-Ca, Heulandite-K, Heulandite-Na, Heulandite-Sr|
Note on the distinguishing differences between heulandite and clinoptilolite (http://www.mineralogicalassociation.ca/doc/abstracts/ima98/ima98(13 [Link Broken? Mar 2013]).pdf ):
"Zeolite mineral species shall not be distinguished solely on the basis of the framework Si : Al ratio. An exception is made in the case of heulandite and clinoptilolite; heulandite is defined as the zeolite mineral series having the distinctive framework topology of heulandite and the ratio Si : Al < 4.0. Clinoptilolite is defined as the series with the same framework topology and Si : Al ≥ 4.0.
Application of the rule
Many zeolites have a widely variable Si : Al ratio, but this, in itself, is not regarded as providing adequate grounds for recognition of separate species. The exception is based on entrenched usage of the names heulandite and clinoptilolite, and their convenience for recognizing an important chemical feature. The cutoff value adopted (following Boles 1972) is arbitrary in a continuous range of compositions. The usual 50% compositional rule cannot be applied, as there are no clearly defined Si,Al end-member compositions for heulandite and clinoptilolite. Thermal stability has been used by some investigators to distinguish clinoptilolite from heulandite. This is a derivative property, however, suggested by Mumpton (1960) as an aid to identification, and it is not appropriate as the basis for definition. Alietti (1972) and Boles (1972) have shown that there is no gap in composition either in framework or extra-framework cation contents between heulandite and clinoptilolite, and that samples transitional in composition show intermediate properties in terms of thermal stability.
The cation content is highly variable. Ca-, Na-, and K-dominant compositions are known, and Sr, Ba, and Mg are in some cases substantial. TSi in the range 0.80–0.84. Minerals with the same framework topology but with TSi < 0.80, Si/Al < 4.0 are classified as heulandite, with which clinoptilolite forms a continuous series. Monoclinic, C2/m, or C2, or Cm.
The cation content is highly variable. Ca-, Na-, K-, and Sr-dominant compositions are known, and Ba and Mg are in some cases substantial. TSi in the range 0.71 to 0.80."
Classification of Heulandite
|Strunz 8th edition ID:||8/.-|
8 : Silicates
|Hey's CIM Ref.:||16.10.19|
16 : Silicates Containing Aluminum and other Metals
10 : Aluminosilicates of Ca and alkalis
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Physical Properties of Heulandite
|Hardness (Mohs):||3 - 3½|
|Density (measured):||2.1 - 2.2 g/cm3|
|Density (calculated):||2.17 g/cm3|
Crystallography of Heulandite
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About Crystal AtlasYou may need to scroll this box using your mouse to view the full instructions.
The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. You need Java to see these. You can download Java for free - click here to download Java
The 3d models and java code are kindly provided by www.smorf.nl. You can control the movement of the models by holding down the left mouse-button over the 3d model and moving your mouse. Keyboard controls are:
|X-Ray Powder Diffraction:|
Radiation - Copper Kα
Data courtesy of RRUFF project at University of Arizona, used with permission.
Optical Data of Heulandite
|RI values:||nα = 1.476 - 1.506 nβ = 1.479 - 1.510 nγ = 1.479 - 1.517|
|2V:||Measured: 10° to 48°|
|Maximum Birefringence:||δ = 0.003 - 0.011|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Dispersion:||r > v|
Relationship of Heulandite to other Species
|Related Minerals - Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Heulandite
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Heulandite
Ventriglia U. (1955) La struttura della heulandite. Periodico di Mineralogia – Roma pp. 49-83.
Merkle, A.B., and M. Slaughter (1968), Determination and refinement of the structure of heulandite: American Mineralogist: 53: 1120-1138.
Alberti, A. (1972), On the crystal structure of the zeolite heulandite: Tschermaks Mineralogische und Petrographische Mitteilungen: 18: 129-146.
Boles, J.R. (1972), Composition, optical properties, cell dimensions and thermal stability of some heulandite group zeolites: American Mineralogist: 57: 1463-1493.
Alberti, A. (1973), The structure type of heulandite B (heat-collapsed phase): Tschermaks Mineralogische und Petrographische Mitteilungen: 19: 173-184.
Alietti, A. (1972), Polymorphism and crystal chemistry of heulandite and Clinoptilolite: Am. Min.: 57: 1448-1462.
Boles, J.R. (1972), Composition, optical properties, cell dimensions and thermal stability of some heulandite group zeolites: Am. Min.: 57: 1463-1493.
Comodi, P., G.D. Gatta, & P.F. Zanazzi (2001), High-pressure structural behavior of heulandite: European Journal of Mineralogy: 15: 247-255.
R. Murao, K. Yubuta, R. Miyawaki and K. Sugiyama (2009): Analysis of aluminoceladonite included in green heulandite. JAKOKA: 2009 Annual Meeting of the Japan Association of Mineralogical Sciences, abs. R4-11, p. 105.
Internet Links for Heulandite
|Specimens:||The following Heulandite specimens are currently listed for sale on minfind.com.|
Localities for Heulandite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
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