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Agrellite

Discovered in 1973;   IMA status: Valid (IMA approved 1976)

Chemistry

Chemical Formula:

NaCa₂(Si₄O₁₀)F

Sodium Calcium Silicate Fluoride

Molecular Weight:

394.48 gm

Composition:

Sodium

5.83 %

Na

7.86 %

Na₂O

Calcium

20.32 %

Ca

28.43 %

CaO

Silicon

28.48 %

Si

60.93 %

SiO₂

Oxygen

40.56 %

O

Fluorine

4.82 %

F

4.82 %

F

—

 — %

F

-2.03 %

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.15-10

Nickel-Strunz 10th Ed. ID:

9.DH.75

9 : SILICATES (Germanates)
D : Inosilicates
H : Inosilicates with 4-periodic single chains, Si₄O₁₂

Related to:

Litidionite Group

Synonyms:

IMA 1973-032

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals elongated [001], to 10 cm; platy aggregates

Twinning:

None

Physical Properties

Cleavage:

[110] Perfect, [110] Perfect, [010] Poor

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5

Density:

2.902 (g/cm³)

Luminescence:

Fluoresces bright pink under LW UV and duller pink under SW UV.

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, Gray-White, Greenish-White

Transparency:

Transparent to Translucent

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.567 - 1.581  Biaxial ( - )

Birefringence:

0.0140

Dispersion:

Strong; r > v

Occurances

Geological Setting:

In pegmatite lenses and pods and in mafic gneisses in a regionally metamorphosed agpaitic alkalic rock complex (Villedieu Township, Canada).

Common Associations:

Biotite, Britholite, Calcite, Clinohumite, Fluorite, Galena, Gittinsite, Hiortdahlite, Miserite, Mosandrite, Norbergite, Phlogopite, Vlasovite, Zircon (Villedieu Township, Canada); Aegirine, Eudialyte, Miserite, Quartz (Wausau, Wisconsin, USA).

Type Locality:

Kipawa alkaline complex, Les Lacs-du-Témiscamingue, Témiscamingue, Abitibi-Témiscamingue, Québec, Canada

Year Discovered:

1973 (IMA approved 1976)

View mineral photos:

Agrellite Mineral Photos and Locations

Unusual Gem Categories

Fluorescent Gems

More Information

Mindat.org
Webmineral.com

Agrellite is a rare silicate mineral that is commonly found with Eudialyte and Aegirine. Its crystals are found as platy, blocky aggregates and so are not suitable for faceting but when combined with Eudialyte, can make beautiful cabochons.

Agrellite is named to honor Professor Stuart Olof Agrell (1913-1996), eminent petrologist, Cambridge University, Cambridge, England.

Agrellite is only found at a few locations including the Sheffield Lake complex, Kipawa River, Villedieu Township, Quebec, Canada; the Wausau complex, Marathon County, Wisconsin, USA; the Dara-i-Pioz massif, Alai Range, Tien Shan, Tajikistan; the Murun massif, southwest of Olekminsk, Yakutia, Russia.

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