Mineral Information and Data:

Aegirine
NaFe3+Si2O6 [CNMNC approved formula]

Named after the Teutonic god of the sea. Acmite is from the Greek "point" in allusion to the pointed crystals.

IMA status : Approved Species 1835 ()
CLASSIFICATION 
Dana
(8th edition) :
65.01.03c.02  
  (65) Inosilicate Single-Width Unbranched Chains, W=1
  (65.01) with chains P=2
  (65.01.03c) C2/c clinopyroxenes (Na clinopyroxenes)
  
Nickel-Strunz
(10th edition) :
09.DA.25
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DA) with 2-periodic single chains, Si2O6; pyroxene family
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: C2/c
Unit cell: a = 9.66 Å, b = 8.80 Å, c = 5.29 Å, b = 107.4°
Crystal Habit: Crystals long prismatic, vertically striated or furrowed; tufts or acicular to capillary.
Twinning: Common on {100}, simple or lamellar
  
Color: Dark green to greenish black
Diaphaneity: Translucent to opaque
Luster: Vitreous to resinous
Hardness (Mohs): 6
Measured Density: 3.50 to 3.60 g/cm3
Cleavage: 2; {110} good; {100} parting
Tenacity: Brittle
Fracture: Uneven
Streak: Pale yellowish gray
  
Geologic Setting: Common in alkalic igneous rocks, carbonatites, and pegmatites. From regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. An authigenic mineral in some shales and marls.
Mineral Association: Potassic feldspar, nepheline, riebeckite, arfvedsonite, aenigmatite, astrophyllite, catapleiite, eudialyte, serandite, apophyllite
  
Synonyms/varieties: Acmite, schefferite (Mn, Fe-rich var.)
Other Properties: Gemstone Unlikely Available.

 

Aegirine
Origin: 3M quarry, Little Rock, Pulaski Co., Arkansas, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Aegirine
Origin: Magnet Cove, Arkansas, U.S.A.
Sample size: 3 x 4 cm
Photo: Dan Weinrich

 

Aegirine
(zoom-in of above)

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