Eudidymite (original) (raw)

A valid IMA mineral species - grandfathered

About EudidymiteHide

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Formula:

Na2Be2Si6O15 · H2O

Crystal System:

Monoclinic

Name:

From the Greek words for well and twinned, in allusion to its common occurrence in twins.

During his visit in the summer of 1887 to Lille Arøya, Langesundsfjorden in Norway, the mineralogist Waldemar Christofer Brøgger (1851-1940) was shown an unknown mineral found by two local collectors. It was showed to be a new mineral and later described by Brøgger (1887, 1890).
The crystal structure was solved by Ito (1947) and Fang et al. (1972).

Note: The type locality, the island Lille Arøya, was called by Brøgger as Ober-Arö or Övre Arö. The contemporary correct name is Lille Arøya.

Unique IdentifiersHide

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Long-form identifier:

mindat:1:1:1421:8

e3c1a915-23df-48f2-944c-13f741a8f9e7

IMA Classification of EudidymiteHide

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Approved, 'Grandfathered' (first described prior to 1959)

Type description reference:

Classification of EudidymiteHide

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9.DG.60

9 : SILICATES (Germanates)
D : Inosilicates
G : Inosilicates with 3-periodic single and multiple chains

66.3.1.3

66 : INOSILICATES Double-Width,Unbranched Chains,(W=2)
3 : Amphiboles - Ca-Na subgroup

14.3.6

14 : Silicates not Containing Aluminum
3 : Silicates of Be

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Physical Properties of EudidymiteHide

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Transparency:

Transparent, Translucent

Comment:

Pearly on cleavages

Cleavage:

Perfect
Perfect on {001}, imperfect on{551}

Density:

2.55 g/cm3 (Measured)

Optical Data of EudidymiteHide

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RI values:

_n_α = 1.545 _n_β = 1.546 _n_γ = 1.551

2V:

Measured: 30° , Calculated: 50°

δ = 0.006

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Dispersion:

r > v distinct

Chemistry of EudidymiteHide

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Mindat Formula:

Na2Be2Si6O15 · H2O

Common Impurities:

Al,Fe,Ca

Crystallography of EudidymiteHide

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Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 12.6188(10) Å, b = 7.3781(5) Å, c = 13.9940(9) Å
β = 103.762(5)°

Ratio:

a:b:c = 1.71 : 1 : 1.897

Morphology:

Crystals tabular on (001), spherulitic, micaceous, coarse and granular,massive.

Twinning:

Twins on {001} common. V-shaped (Swallowtwins) twin

Crystallographic forms of EudidymiteHide

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Crystal Atlas:

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3d models and HTML5 code kindly provided bywww.smorf.nl.

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Crystal StructureHide

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X-Ray Powder DiffractionHide

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Radiation - Copper Kα

Data Set:

Data courtesy of RRUFF project at University of Arizona, used with permission.

Powder Diffraction Data:

Geological EnvironmentHide

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Type Occurrence of EudidymiteHide

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General Appearance of Type Material:

Tabular crystals, usually twinned on {001}

Chemical Analysis of Type Material:

Geological Setting of Type Material:

Associated Minerals at Type Locality:

Reference:

Brøgger, W.C. (1887). Om ”Eudidymit”, et nyt norsk mineral. Forelöbig meddelelse. Nyt Magazin for Naturvidenskaberne, 31, 196-199

Other Language Names for EudidymiteHide

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Simplified Chinese:双晶石

Traditional Chinese:雙晶石

Common AssociatesHide

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Associated Minerals Based on Photo Data:

Related Minerals - Strunz-mindat GroupingHide

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Other InformationHide

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Health Risks:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Internet Links for EudidymiteHide

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References for EudidymiteHide

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Reference List:

Gatta, G. D., Rotiroti, N., McIntyre, G.J., Guastoni, A., Nestola, F. (2008) New insights into the crystal chemistry of epididymite and eudidymite from Malosa, Malawi: A single-crystal neutron diffraction study. American Mineralogist, 93 (7) 1158-1165 doi:10.2138/am.2008.2965

Larsen, Alf Olav, Andersen, Frode, Dahlgren, Sven, Larsen, Knut Edvard, Burvald, Ingulv - Ed. (2010) The Langesundsfjord - History, geology, pegmatites, minerals. Bode Verlag Gmbh. p.1-240.

Localities for EudidymiteHide

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This 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.

Locality ListHide

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- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.