Editorial Feature

Agrellite – Occurrence, Properties, and Distribution

Jun 12 2014

Agrellite was named after Professor Stuart Olof Agrell, an eminent petrologist from Cambridge University in Cambridge, England.

Properties of Agrellite

The following are the key properties of Agrellite:

Cell Data
- Space group: P1
- a = 7.759(2)
- b = 18.946(3)
- c = 6.986(1)
- α = 89.88(2) °
- β = 99.61°
- γ = 94.2(2)°
- Z = 4

Crystal Data
- Triclinic
- Point group: 1
- Elongated || [001], to 10cm
- Platy aggregates
- X-ray powder pattern: 3.19 (vs), 3.14 (vs), 3.44 (s), 3.33 (s), 2.58 (s), 2.31 (s), 2.04 (ms)

Chemical Composition

Elements	Content 1	Content 2
SiO₂	57.79	60.92
CaO	25.70	28.43
Na₂O	7.90	7.86
F	4.45	4.82
RE	2.57	-
-O = F₂	1.87	2.03
Al₂O₃	1.32	-
H₂O+	0.4	-
MnO	0.25	-
K₂O	0.22	-
ZrO₂	0.18	-
SrO	0.16	-
Fe₂O₃	0.11	-
BaO	0.06	-
MgO	0.02	-
TiO₂	0.01	-
Total	99.27	100.00

Optical Properties
- Optical class: Biaxial (-)
- α = 1.567; β = 1.579; γ = 1.581

Estimated Properties

Electron density	Bulk density (electron density) = 2.84 g/cm³ note: Specific gravity of Agrellite = 2.86 g/cm³
Photoelectric	PE_Agrellite = 3.71 barns/electron U = PE_Agrellite x ρ electron density = 10.54 barns/cm³
Fermion index	Fermion index = 0.01 Boson index = 0.99
Radioactivity	Agrellite is not radioactive

How to Identify Agrellite

Agrellite can be identified in the field by its color variations, such as white, grayish-white, and greenish-white. Its translucent form has {110} perfect, {110} perfect, {010} poor cleavage. This mineral has a vitreous–pearly luster, with a white streak.

The density of agrellite is 2.88 to 2.9 g/cm³, with a hardness of 5.5 – approximate to a knife blade.

Global Distribution

Agrellite is distributed in the following places:

USA - In the Wausau complex, Marathon Co. Wisconsin
Canada - From the Sheffield Lake complex, Kipawa River, Villedieu Township, Quebec
Tajikistan - In the Dara-i-Pioz massif, Alai Range, Tien Shan
Russia - From the Murun massif, south-west of Olekminsk, Yakutia

Occurrence of Agrellite and Useful Mineral Association

Agrellite occurs in pegmatite lenses and pods, and in mafic gneisses in a regionally metamorphosed agpaitic alkalic rock complex.

It is often associated with minerals such as mosandrite, britholite, hiortdahlite, vlasovite, calcite, fluorite, norbergite, zircon, biotite, clinohumite, gittinsite, phlogopite, miserite, aegirine, galena, eudialyte, quartz, and miserite.