A single
crystal of Aegirine showing a tapering termination and striations parallel to
the "C" axis (long axis).
Single,
tapering crystals of Aegirine in Orthoclase.
This is a microscopic view of the single crystal from the above image.
Note the striations parallel to the long axis of the crystal and the slight
greenish cast.
Radiating prismatic blades
CHEMISTRY - NaFeSi2O6
CRYSTALLOGRAPHY - Monoclinic
CRYSTAL GROWTH AND HABITS - Typically prismatic with either blunt or tapering terminations. It usually has striations along its long axis. Aegirine is commonly found in acicular sprays or sometimes as radiating masses.
COLOR AND OPTICAL PROPERTIES - Most commonly Aegirine is dark green to black but can also be reddish brown. It is translucent to opaque.
HARDNESS - 6
SPECIFIC GRAVITY - 3.5 - 3.6
LUSTER - Vitreous
STREAK - Light yellowish gray
BREAKABILITY - Aegirine has a good cleavage along {110} and a parting along the {100}; it has an uneven fracture and is brittle.
OCCURRENCE - Aegirine is typically found in alkali igneous rocks and in associated pegmatites and in carbonatites.
ASSOCIATED MINERALS - Orthoclase, Nepheline, Riebeckite, Astrophyllite, Eudialyte
MINERAL NAME - The name is derived from the Scandinavian god of the sea "Aegir".