Aenigmatite
Encyclopedia
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, pegmatite
s, and granite
s 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 on March 1980 in South Yemen. Other notable studied occurrences include:
Pantelleria
Pantelleria , the ancient Cossyra, is an Italian island in the Strait of Sicily in the Mediterranean Sea, southwest of Sicily and just east of the Tunisian coast. Administratively Pantelleria is a comune belonging to the Sicilian province of Trapani...
, is a sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
inosilicate
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...
mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
. 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
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 3.74 to 3.85. Aenigmatite forms a solid-solution series with wilkinsonite, Na2Fe2+4Fe3+2Si6O20.
Aenigmatite is primarily found in peralkaline
Peralkaline
Peralkaline rocks include those igneous rocks which have a deficiency of aluminium such that sodium and potassium are in excess of that needed for feldspar. The presence of aegerine and riebeckite are indicative of peralkaline conditions....
volcanic rocks, pegmatite
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
s, and granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
s as well as silica-poor intrusive rocks. It was first described by August Breithaupt
August Breithaupt
Johann Friedrich August Breithaupt was a German mineralogist and professor at Freiberg Mining Academy in Freiberg, Saxony.-Biography:...
in 1865 for an occurrence in the Ilimaussaq intrusive complex
Ilimaussaq intrusive complex
The Ilimaussaq intrusive complex is a large alkalic layered intrusion located on the southwest coast of Greenland. It is Mesoproterozoic in age. It is the type locality of agpaitic nepheline syenite and hosts a variety of unusual rock types....
of southwest Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
. Its name comes from αίνιγμα, the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word for "riddle".
It was also reported from the Kaidun meteorite
Kaidun meteorite
Kaidun is a meteorite that fell on 3 December 1980 on a Soviet military base near what is now Al-Khuraybah in Yemen. A fireball was observed travelling from the northwest to the southeast, and a single stone weighing about 2 kilograms was recovered from a small impact pit...
, possibly a Mars meteorite
Mars meteorite
A martian meteorite is a rock that formed on the planet Mars, was ejected from Mars by the impact of an asteroid or comet, and landed on the Earth. Of over 53000 meteorites that have been found on Earth, 99 are martian...
, which landed on March 1980 in South Yemen. Other notable studied occurrences include:
- Narsaarsuk and elsewhere in Greenland.
- The KhibinyKhibiny MassifThe Khibiny Massif, Khibiny Mountains, Khibinsky Mountains or Khibins, Khibinsky tundras, Khibiny is one of the two main mountain ranges of the Kola Peninsula, Russia, within the Arctic Circle, located between Imandra and Umbozero lakes.The massif is of oval shape of about 1,300 sq.km...
and Lovozero alkaline massifs on Kola PeninsulaKola PeninsulaThe Kola Peninsula is a peninsula in the far northwest of Russia. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely to the north of the Arctic Circle and is washed by the Barents Sea in the north and the White Sea in the east and southeast...
, RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. - The volcanic island of PantelleriaPantelleriaPantelleria , the ancient Cossyra, is an Italian island in the Strait of Sicily in the Mediterranean Sea, southwest of Sicily and just east of the Tunisian coast. Administratively Pantelleria is a comune belonging to the Sicilian province of Trapani...
, ItalyItalyItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. - In the USA, from Granite Mountain, near Little Rock, Pulaski County, Arkansas, and Santa RosaSanta Rosa, CaliforniaSanta Rosa is the county seat of Sonoma County, California, United States. The 2010 census reported a population of 167,815. Santa Rosa is the largest city in California's Wine Country and fifth largest city in the San Francisco Bay Area, after San Jose, San Francisco, Oakland, and Fremont and 26th...
, Sonoma County, CaliforniaSonoma County, CaliforniaSonoma County, located on the northern coast of the U.S. state of California, is the largest and northernmost of the nine San Francisco Bay Area counties. Its population at the 2010 census was 483,878. Its largest city and county seat is Santa Rosa....
. - In Australia, from WarrumbungleWarrumbunglesThe Warrumbungles is the name of a mountain range and National Park located in northern New South Wales, Australia. The nearest town to the Warrumbungles is Coonabarabran...
volcano, Nandewar volcano, and the Mount Warning complex, New South Wales; and the Peak Range Province, Queensland. - In Canada, from Mount EdzizaMount Edziza volcanic complexThe Mount Edziza volcanic complex is a large and potentially active north-south trending complex volcano in Stikine Country, northwestern British Columbia, Canada, located southeast of the small community of Telegraph Creek...
, the IlgachuzIlgachuz RangeThe Ilgachuz Range is a name given to an extinct shield volcano in British Columbia, Canada. It is not a mountain range in the normal sense, because it was formed as a single volcano that has been eroded for the past 5 million years. It lies on the Chilcotin Plateau, located some north-northwest...
and Rainbow RangeRainbow Range (Coast Mountains)The Rainbow Range, formerly known as the Rainbow Mountains, is a mountain range in British Columbia, Canada, located northwest of Anahim Lake...
shield complexes. - From Logan Point quarry, Dunedin volcano, New Zealand.