Astrophyllite - Encyclopedia

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Triclinic
    Chemistry : (K,Na)3 (Fe,Mn)7 Ti2Si8O24 (O,OH)7
    Rarity : Uncommon

Astrophillite is a complex silicate of iron, potassium and titanium in which iron can be completely replaced by manganese, forming a continuous series with kupletskite ; titanium can also be substituted by niobium or zirconium. It takes its name from the Greek astron (star) and phullon (leaf) because of its foliated look and brilliant luster. It is a classic silicate of alkaline rocks, mainly sodalite and nepheline syenites and their pegmatites, more rarely fenites. It accompanies sodalite, nepheline and aegyrine. Astrophyllite resembles a brown biotite : the crystals are usually lamellar with hexagonal or rhombic contours, frequently united in radiating aggregates, with a perfect basal cleavage. The color is brown, sometimes brown-yellow. Unlike micas, astrophyllite crystals are brittle and non-flexible. It is a mineral that can be cut in cabochon for jewelery.

41.00 ct astrophyllite from the Kola Peninsula, Russia
34.50 ct astrophyllite from the Kola Peninsula, Russia
24.80 ct astrophyllite from the Kola Peninsula, Russia
32.00 ct astrophyllite from the Kola Peninsula, Russia

Astrophyllite in the World

Astrophyllite crystals up to 10 cm were found in the alkaline syenites of the Ilimaussaq complex near Narssaq (Greenland), Mount St-Hilaire (Canada), and in the nepheline syenite Kola peninsula in Russia (Lovozero, Khibiny).

Astrophyllite in France

In France, astrophyllite is present in the alkaline granites of southern Corsica (Evisa, near Porto).

Fakes and scams :

No fake inventories for this mineral species.

Hardness : 3
Density : 3.2 to 3.4
Fracture : Irregular
Streak : Brown

TP : Opaque to translucent
IR : 1.680 to 1.730
Birefringence : 0.050
Pleochroism : Weak
Fluorescence : None

Solubility : Hydrofluoric acid

Magnetism : Paramagnetic
Radioactivity : None