Krotite is a natural

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

composed of

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, with the molecular formula CaAl₂O₄. It is the low-pressure dimorph of CaAl₂O₄, of which the high-pressure dimorph is named dmitryivanovite. Krotite was reported in 2011 in a calcium-aluminium-rich inclusion (CAI) in the carbonaceous chondrite meteorite NWA (North West Africa) 1934, which landed in

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...

. The mineral name was approved by the International Mineralogical Association (IMA 2010-038) and honors Alexander N. Krot, a researcher in

cosmochemistry Cosmochemistry (from Greek κόσμος ''kósmos'', "universe" and χημεία ''khemeía'') or chemical cosmology is the study of the chemical composition of matter in the universe and the processes that led to those compositions. This is done ...

at the

University of Hawaii at Manoa A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

in Honolulu, Hawaii. Researchers have found that the mineral, which has the same atomic arrangement as a man-made component of some types of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

(specifically,

calcium aluminate cements Calcium aluminate cements are cements consisting predominantly of hydraulic calcium aluminates. Alternative names are "aluminous cement", "high-alumina cement" and "Ciment fondu" in French. They are used in a number of small-scale, specialized ap ...

), forms under low

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

at a

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

of at least . These conditions of high temperature and low pressure are consistent with a hypothesis that the krotite grains found in the meteorite formed as high-temperature

condensate Condensate may refer to: * The liquid phase produced by the condensation of steam or any other gas * The product of a chemical condensation reaction, other than water * Natural-gas condensate, in the natural gas industry * ''Condensate'' (album) ...

s from the solar nebula from which the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

formed, approximately 4.6 billion years ago. Thus, they are likely to be among the earliest minerals formed in the solar system. The CAI containing the krotite was said to resemble a "cracked egg" because its rim was crosscut by cracks filled with

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

and

aluminum hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric, i.e., it has both basic an ...

s. Researchers suggest that the mineral assemblage in the CAI was at one time surrounded by a hot

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

that reacted with krotite crystals on the surface of the CAI. It is likely that cracks on this rim of the CAI were filled with hydrated oxides as a result of

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...

that occurred after the meteorite landed on Earth. Associated minerals include

perovskite Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (chemical formula ). Its name is also applied to the class of compounds which have the same type of crystal structure as (XIIA2+VIB4+X2−3), known a ...

gehlenite Gehlenite, (Ca2Al lSiO7, is a sorosilicate, Al-rich endmember of the melilite complete solid solution series with akermanite.Deer et al., 1993 The type locality is in the Monzoni Mountains, Fassa Valley in Trentino in Italy, and is named after ...

hercynite Hercynite is a spinel mineral with the formula FeAl2O4. It occurs in high-grade metamorphosed iron rich argillaceous sediments as well as in mafic and ultramafic igneous rocks. Due to its hardness it also is found in placers. It was first descr ...

mayenite Chlormayenite (after Mayen, Germany), Ca12Al14O32 ��4Cl2 is a rare calcium aluminium oxide mineral of cubic symmetry. It was originally reported from Eifel volcanic complex (Germany) in 1964. It is also found at pyrometamorphic sites such a ...

grossite Grossite is a calcium aluminium oxide mineral with formula CaAl4O7. It is a colorless to white vitreous mineral which crystallizes in the monoclinic crystal system. Grossite was first described 1994 for an occurrence in the Hatrurim Formation of ...

hibonite Hibonite is a mineral with the chemical formula , occurring in various colours, with a hardness of 7.5–8.0 and a hexagonal crystal structure. It is rare, but is found in high-grade metamorphic rocks on Madagascar. Some presolar grains in primiti ...

, spinel and

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...

References

{{Meteorites Calcium minerals Aluminium minerals Oxide minerals Meteorite minerals Monoclinic minerals Minerals in space group 14

See also

References