L6–7 (troilite–metalElement that readily forms cations and has metallic bonds; sometimes said to be similar to a cation in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. A diagonal line drawn Click on Term to Read More nodule bearing) click on photo for a magnified view Fell May 22, 2012 21° 16′ 09′ N., 78° 34′ 49′ E., main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass". Click on Term to Read More In 2012, May 22 at approximately 2:30 P.M., a fireballA fireball is another term for a very bright meteor, generally brighter than magnitude -4, which is about the same magnitude of the planet Venus as seen in the morning or evening sky. A bolide is a special type of fireball which explodes in a bright terminal flash at its end, often with visible fragmentation. Click on Term to Read More accompanied by detonations was seen and heard by local residents as it streaked over the Akola and Nagpur districts of India, moving in a generally eastward direction. At the same time, the Broadband Seismic Observatory of the Geological Survey of India recorded a 2.1 magnitude seismic event lasting 90 seconds, which was centered 30 kms ENE of Akola. Several meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More fragments were quickly recovered by residents in and around Katol.
Four fragments were recovered initially by residents at different locations, and these were documented by a team of geoscientists led by Binod Kumar: 1) the largest fragment, weighing 673.5 g, was found at Lakshmi Nagar by Nathoji Ramakrishna Charde; 2) a 74.4 g fragment was found near Khutamba road by Javed Razzak Shaikh after it penetrated the galvanized metal roof of a shed, damaging the concrete floor below; 3) a fragment was found at IUDP Layout by Govinda Muralidhar Mahajan that had penetrated 10 cm into the soil; and 4) a fragment was found at IUDP Layout towards Nagpur road by Pundlik Kashiram Shivarkar. It is now reported that more than 30 fragments have been recovered, having a combined weight of ~13 kg (Ghosh and Murty, 2014).
Extensive analyses of this unique meteorite were conducted at research facilities in both India (Geological Survey of India; Physical Research Laboratory; National Geophysical Research Institute) and America (Center for Meteorite Studies at Arizona State University; Institute of MeteoriticsScience involved in the study of meteorites and related materials. Meteoritics are closely connected to cosmochemistry, mineralogy and geochemistry. A scientist that specializes in meteoritics is called a meteoriticist. Click on Term to Read More at University of New Mexico), eventually being published in the 2013 Meteoritical Bulletin #102 classified as an L6 chondriteChondrites are the most common meteorites accounting for ~84% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), reduced Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such Click on Term to Read More.
An independent classification of Katol was published by Ghosh and Murty (Physical Research Laboratory, India) at the 45th LPSC, #1300 (2014). Here, Katol was classified as a shock-melted L6–7 ordinary chondriteWork in Progress Ordinary chondrites (OCs) are the largest meteorite clan, comprising approximately 87% of the global collection and 78% of all falls (Meteoritical Society database 2018)1. Meteorites & the Early Solar System: page 581 section 6.1 OC of type 5 or 6 with an apparent shock stage of S1, Click on Term to Read More, the first such brecciaWork in Progress ... A rock that is a mechanical mixture of different minerals and/or rock fragments (clasts). A breccia may also be distinguished by the origin of its clasts: (monomict breccia: monogenetic or monolithologic, and polymict breccia: polygenetic or polylithologic). The proportions of these fragments within the unbrecciated material Click on Term to Read More ever described. Although they report observing no discernable chondrulesRoughly spherical aggregate of coarse crystals formed from the rapid cooling and solidification of a melt at ~1400 ° C. Large numbers of chondrules are found in all chondrites except for the CI group of carbonaceous chondrites. Chondrules are typically 0.5-2 mm in diameter and are usually composed of olivine Click on Term to Read More in the light-gray, recrystallized silicateThe most abundant group of minerals in Earth's crust, the structure of silicates are dominated by the silica tetrahedron, SiO44-, with metal ions occurring between tetrahedra). The mesodesmic bonds of the silicon tetrahedron allow extensive polymerization and silicates are classified according to the amount of linking that occurs between thematrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents. Click on Term to Read More (primarily composed of olivineGroup of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion Click on Term to Read More and low-Ca pyroxeneA class of silicate (SiO3) minerals that form a solid solution between iron and magnesium and can contain up to 50% calcium. Pyroxenes are important rock forming minerals and critical to understanding igneous processes. For more detailed information, please read the Pyroxene Group article found in the Meteoritics & Classification category. Click on Term to Read More), they did findMeteorite not seen to fall, but recovered at some later date. For example, many finds from Antarctica fell 10,000 to 700,000 years ago. Click on Term to Read More rare microchondrules. Minor phases include plagioclaseAlso referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite Click on Term to Read More (mostly transformed to maskelyniteNatural glass composed of isotropic plagioclase produced during shock metamorphism (not melting) at pressures of ~30 GPa. Maskelynite is commonly found in shergottites though also found in some ordinary chondrites, HED and lunar meteorites. It is also found in association with meteorite impact craters and crater ejecta. Named after British Click on Term to Read More), troiliteBrass colored non-magnetic mineral of iron sulfide, FeS, found in a variety of meteorites. Click on Term to Read More, FeN-metal, high-Ca pyroxene, merrillite, and chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More. While specks of FeN-metal and troilite are ubiquitous throughout the meteorite, an ~2 cm-sized, shock-melted, multi-textured troilite–metal nodule was described as a shock-generated fragmental breccia.
The troilite–metal nodule is composed of a complex intergrowth of most of the same components present in the bulk meteorite, but with the addition of various high-pressure phases including wadsleyiteHigh pressure polymorph of olivine, β-Mg2SiO4, found on Earth and in some meteorites. It is thought to make up 50% or more of Earth's mantle between depths of 400 and 525 km. Wadsleyite transforms into ringwoodite at high pressure, but the exact pressure depends strongly on composition. At lower pressures, and ringwooditeHigh-pressure olivine polymorph with a spinel structure that is found in highly shocked meteorites (above ~50 GPa, shock level > S5) and the Earth's transition zone mantle (~13 GPa). Under even higher pressure in the lower mantle (~24 GPa), ringwoodite decomposes into perovskite (Mg,Fe)SiO3, and magnesiowüstite (Mg,Fe)O, whose properties are Click on Term to Read More (Ray et al., 2014). These high-pressure phases correspond to shock pressures of at least 45 GPa (S5) and temperatures in the range of 900–1500°C. In addition, the presence of a complex network of sub-mm to µm-scale shear-stress-induced melt veins with interconnected metal-sulfide melt pockets, as well as silicate grains with planar deformation features, attests to a shock-heating event in which some localized shock pressures approached ~90 GPa (S6+). Based on microtextural evidence such as the quench-texture of the troilite–metal nodule, it was inferred by Ray et al. (2017) that the nodule was formed in a severe impact long after the chondritic host rock had become thermally metamorphosed to type 6–7, and that it was incorporated into the host rock during brecciationThe formation of a breccia through a process by which rock fragments of of various types are recemented or fused together. Click on Term to Read More processes prior to ejection from the parent bodyThe body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. Click on Term to Read More.
Through measurements of the 60Co and 36Cl abundances, Murty et al. (2014) calculated the pre-atmospheric diameter of the Katol meteoroidSmall rocky or metallic object in orbit around the Sun (or another star). to have been 1.7–3.4 m. Based on cosmogenic noble gasElement occurring in the right-most column of the periodic table; also called "inert" gases. In these gases, the outer electron shell is completely filled, making them very unreactive. Click on Term to Read More studies, they determined the CRE age to be 50 (±5) m.y. The specimen of Katol shown above is a 1.17 g partial slice.