THE MINERAL AEGIRINE

Chemistry: NaFeSi2O6 , Sodium Iron Silicate.
Class: Silicates
Subclass: Inosilicates
Group: Pyroxenes
Uses: Only as mineral specimens.
Specimens

Aegirine, which is listed in some guides as acmite, forms impressive crystals that have become classics among collectors. These tall opaque monument-like crystals that jut majestically out from their host rocks are simply splendid. The steeply inclined pyramid on top of the prismatic crystals is very characteristic and thus diagnostic of aegirine. Its alternate name, acmite, comes from the Greek word for point. The name aegirine is after the Teutonic god of the sea, Aegir, and was given when the first specimens of the mineral were discovered in Norway.

Aegirine is difficult to distinguish from its close cousin augite. Under normal circumstances, the steep pyramids of aegirine are the only point of differentiation (excuse the pun).

PHYSICAL CHARACTERISTICS:

Color is black to greenish or brownish black.
Luster is vitreous.
Transparency: Specimens are generally opaque to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include long prismatic crystals terminated by a steep asymmetrical pyramid. Also as disseminated grains, compact and fibrous.
Cleavage is perfect in two directions at near 90 degree angles.
Fracture is uneven.
Hardness is 6 - 6.5
Specific Gravity is approximately 3.5 - 3.6 (above average for translucent minerals)
Streak is white or gray.
Other Characteristics: Splinters or thin edges are translucent green.
Associated Minerals are augite, nepheline, andradite, barite, quartz, spessartine, riebeckite, biotite, sodalite and albite
Notable Occurrences include Mont Saint-Hilaire, Quebec, Canada; Kongsberg, Norway; Narsarssuk, Greenland; Kola Peninsula, Russia; Magnet Cove Arkansas, USA; Kenya; Scotland and Nigeria.
Best Field Indicators are crystal habit (especially its steep pyramids), density, cleavage, color and hardness.