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Eudialyte

iscovered in 1819;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Na₄(Ca,Ce)₂(Fe++,Mn,Y)ZrSi₈O₂₂(OH,Cl)₂

Sodium Calcium Cerium Iron Manganese Zirconium Silicate Hydroxide Chloride

Molecular Weight:

992.15 gm

Composition:

Sodium

9.27 %

Na

12.49 %

Na₂O

Calcium

6.06 %

Ca

8.48 %

CaO

Cerium

7.06 %

Ce

8.27 %

Ce₂O₃

Yttrium

0.90 %

Y

1.14 %

Y₂O₃

Zirconnium

9.19 %

Zr

12.42 %

ZrO₃

Manganese

1.66 %

Mn

2.14 %

MnO

Iron

3.38 %

Fe

4.34 %

FeO

Silicon

22.65 %

Si

48.45 %

SiO₂

Hydrogen

0.15 %

H

1.36 %

H₂O

Chlorine

1.79 %

Cl

1.79 %

Cl

―

―   %

Cl

-0.40 %

-O=Cl₂

Oxygen

37.90 %

O

100.00 %

100.48 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/E.23-10

Nickel-Strunz 10th Ed. ID:

9.CO.10

9 : SILICATES (Germanates)
B : Cyclosilicates
O : [Si₉O₂₇]₁₈- 9-membered rings

Related to:

Eudialyte Group

Members of Group:

Eudialyte Group: Alluaivite, Andrianovite, Aqualite, Carbokentbrooksite, Davinciite, Dualite, Eudialyte, Feklichevite, Fengchengite, Ferrokentbrooksite, Georgbarsanovite, Golyshevite, Hydrorastsvetaevite, Ikranite, Ilyukhinite, Johnsenite-(Ce), Kentbrooksite, Khomyakovite, Labyrinthite, Manganoeudialyte, Manganokhomyakovite, Mogovidite, Oneillite, Raslakite, Rastsvetaevite, Siudaite, Taseqite, Voronkovite, Zirsilite-(Ce)

Varieties:

Manganoeudialyte, Eucolite

Synonyms:

Almandine spar, Eudialite, Eudyalite, Saami Blood

Crystal Data

Crystallography:

Trigonal - Hexagonal - Scalenohedral

Crystal Habit:

Crystals short rhombohedral to long prismatic up to 10 cm. More commonly as irregular masses and vein filings.

Twinning:

None

Physical Properties

Cleavage:

Perfect. Distinct on {0001}, imperfect on {1010} and {1014} {1120}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

2.74 - 3.10 (g/cm³)

Luminescence:

None

Radioactivity:

Mild; GRapi = 7,287.91 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Variable: Carmine-red, orange-red, orange, pink, cherry-red, brownish-red, yellowish-brown, brown, yellow, violet, green

Transparency:

Transparent to Translucent

Luster:

Vitreous to Dull

Refractive Index:

1.606 - 1.613  Uniaxial ( + or - )

Birefringence:

0.003 - 0.010

Dispersion:

n/a

Pleochroism:

Weak

Occurances

Geological Setting:

In nepheline syenites, alkalic granites, and associated pegmatites; may be a major constituent, of both magmatic and late-stage pneumatolytic origin.

Common Associations:

Aegirine, Aenigmatite, Agrellite, Albite, Gittinsite, Vlasovite, Microcline, Mosandrite-(Ce), Nepheline, Vlasovite

Common Impurities:

K, Mg, Sr, TR, Ti, Nb, Al, F, P, S

Type Locality:

Kangerdluarssuq (Kangerdluarsuk) Firth, Ilimaussaq complex, Narsaq, Kitaa (West Greenland) Province, Greenland

Year Discovered:

1819

View mineral photos:

Eudialyte Mineral Photos and Locations

Unusual Gem Categories

Radioactive Gems

More Information

Mindat.org
Webmineral.com

Eudialyte is a principal member of the Eudialyte Group of minerals that includes Eudialyte, Johnsenite-(Ce) and Kentbrooksite plus many other non-gem type minerals. Eudialyte was first described in 1819 by German chemist Friedrich Stromeyer (1776 - 1835) as one of the major constituents of nepheline syenites from the Ilímaussaq Complex, Greenland. In 1832 the mineral Stromeyerite was named in his honor by French mineralogist François Sulpice Beudant (1787 - 1850). The name Eudialyte is from the Greek words eu meaning well and dialytos meaning decomposable, referring to its easy solubility in acids.

Eudialyte is very rarely found as crystals clean enough for faceting and faceted gems are always small and usually included. It is mostly available as cabochons featuring its beautiful colors of reds and pinks contrasted with black Aegirine and white Albite.

Eudialyte may be mildly radioactive due to the presence of Cerium (Ce).

Major sources of Eudialyte material are the Kola Peninsula in Russia and in Canada at Mont Saint-Hilaire and the Kipawa Complex at Sheffield Lake.

Eudialyte gems for sale: