X = yellow brown; Y = red-brown; Z = dark brown to black
2V angle
Measured: 27° to 55°
Dispersion
r < v; very strong
References
[2][3][4]
Aenigmatite, also known as cossyrite after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula is Na2Fe2+5TiSi6O20 and its structure consists of single tetrahedral chains with a repeat unit of four and complex side branches. It forms brown to black triclinic lamellar crystals. It has Mohs hardness of 5.5 to 6 and specific gravity of 3.74 to 3.85. Aenigmatite forms a solid-solution series with wilkinsonite, Na2Fe2+4Fe3+2Si6O20.
Aenigmatite is primarily found in peralkaline volcanic rocks, pegmatites, and granites as well as silica-poor intrusive rocks. It was first described by August Breithaupt in 1865 for an occurrence in the Ilimaussaq intrusive complex of southwest Greenland. Its name comes from αίνιγμα, the Greek word for "riddle".
It was also reported from the Kaidun meteorite, possibly a Mars meteorite, which landed in March 1980 in South Yemen. Other notable studied occurrences include:
Narsaarsuk and elsewhere in Greenland.
The Khibiny and Lovozero alkaline massifs on Kola Peninsula, Russia.
The Yenisei Range, Krasnoyarsk Krai, Russia.
The volcanic island of Pantelleria, Italy.
In the United States, from Granite Mountain, near Little Rock, Pulaski County, Arkansas, and Santa Rosa, Sonoma County, California.
In Australia, from Warrumbungle volcano, Nandewar volcano, and the Mount Warning complex, New South Wales; and the Peak Range Province, Queensland.
In Canada, from Mount Edziza, the Ilgachuz and Rainbow Range shield complexes.
From Logan Point quarry, Dunedin Volcano, New Zealand.
Aenigmatite, also known as cossyrite after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula...
association with potassic feldspar, nepheline, riebeckite, arfvedsonite, aenigmatite, astrophyllite, catapleiite, eudialyte, serandite and apophyllite. Localities...
strongly peralkaline rocks. Mafic minerals may include aegirine, fayalite, aenigmatite, ilmenite, and sodic amphibole (often arfvedsonite or ferrorichterite)...
star (crystals are generally separated and have different lengths). aenigmatite, atacamite, epidote, pyrophyllite, stibnite Reticulated Crystals forming...
rare minerals and is the type locality for thirty minerals, including: aenigmatite, arfvedsonite, sodalite, eudialyte and tugtupite. The complex has an...
Dorrite is a silicate mineral that is isostructural to the aenigmatite group. It is most chemically similar to the mineral rhönite [Ca2Mg5Ti(Al2Si4)O20]...
feldspathoid mineral in addition to nepheline. Reddish-brown to black aenigmatite occurs also in these rocks. Extremely iron-rich olivine is rare, but...
containing chromium, magnesium, oxygen, silicon, and sodium, of the aenigmatite group. "It has been discovered within graphite nodules in three iron...
matrix of sodic plagioclase alkali feldspar, katophorite, arfvedsonite, aenigmatite and opaque oxides that is embedded with sparse phenocrysts of anorthoclase...
January 22, 2009. Yagi, Kenzo; Souther, Jack Gordon (1 August 1974). "Aenigmatite from Mt. Edziza, British Columbia, Canada". American Mineralogist. 59...
phonolite and trachyte; phenocryst phases found in the pantellerite include aenigmatite, anorthoclase, fayalite, hedenbergite, ilmenite and quartz. A blue ice...
of volcanic rocks at Mount Waesche. Phenocrysts at Chang Peak include aenigmatite, alkali feldspar, ilmenite and quartz and at Mount Waesche olivine, plagioclase...
mineral groups and supergroups sharing the same name: sapphirines (aenigmatite, rhönite and sapphirine groups; IMA2008 s.p.), pharmacosiderites (ivanyukite...