Amphibole: first occurrence in a meteorite

This is the first report of an amphibole mineral found in any meteorite. The amphibole richterite (soda tremolite), Na(2)Ca(Mg, Fe)(5)Si(8)O(22)(OH, F)(2), occurs as a primary (preterrestrial) mineral enclosed within graphite nodules in the iron meteorite from Wichita County, Texas.     

Butler, missouri: an unusual iron meteorite

The Butler iron meteorite has been found to have, with respect to other iron meteorites, an unusually high cobalt content (1.4 percent by weight), unusually high germanium contents in the kamacite and the taenite phases, and an unusually low cooling rate (0.5 degrees C/10(6) years). It is suggested that Butler formed in a different environment from that of the rest of the iron meteorites.     

Discovery of an unmelted h-chondrite inclusion in an iron meteorite

The link between H chondrites and silicate inclusions in group IIE iron meteorites has long been suspected, but direct evidence for a common parentage has remained elusive. The discovery of an unmelted chondritic inclusion in the Techado iron meteorite sheds light on the genetic relation between these two groups, providing clues on the origin of chondritic materials as inclusions in iron meteorites. It is proposed that the complex IIE iron meteorite breccias formed by collisions with several different bodies, followed by deep burial of metal and silicate fragments in the asteroidal megaregolith.     

Butler, missouri: an iron meteorite with extremely high germanium content

The Butler iron meteorite has been found to have a germanium concentration of 2000 parts per million, which is about five times higher than the highest concentration that has been measured previously in an iron meteorite. The gallium concentration is 87 parts per million, which is among the highest concentrations found in these objects. The nickel content is 16.0 percent, the second highest nickel concentration known in a meteorite displaying a Widman st?tten pattern. The high Ge/Ni ratio, as well as the association of a high nickel content with high gallium and germanium contents, make this object an exception to two geochemical generalizations regarding the iron meteorites.     

Garnet: first occurrence in the lunar rocks

Three grains of almandine-rich garnet isolated from lunar sample 12021 have the composition Alm(70.7)Gro(25.0)Sp(2.7)Pyr(1.6), with cell edge of 11.624 angstroms and refractive index of 1.81. The garnet probably formed late in the crystallization sequence.     

Chondrules: suggestion concerning the origin

The millimeter-sized, sometimes glassy spheroids called chondrules that occur abundantly in stony meteorites may have been produced by lightning in the primitive Laplaciantype nebula while earthy materials were condensing and collecting to form the asteroids and the terrestrial planets.     

Potassium-feldspar phenocrysts in the surface of colomera, and iron meteorite

Silicate aggregates, including large single crystals of potassium feldspar as long as 11 centimeters and sodium feldspar, are embeded in the surface of the medium octahedrite Colomera. Silicate nodules in the interior appear to be much smaller (about 0.3 centimeter). Glass nodules are abundant both on the external surface and in the interior. These observations are evidence that some iron meteorites formed as segregations within a silicate matrix and did not originate in a metallic core.     

Chondrules: An Origin by Impacts between Dust Grains

A barred chondrule in the Ngawi meteorite contains a magnetite spherule embedded in it. The collision between these two objects fractured and partially remelted the chondrule, an indication that the impact velocity was 10(5) to 10(6) centimeters per second. This observation supports Cameron's and Whipple's recent predictions that grains achieved high velocities in the nebula and that the resulting impacts provide a suitable chondrule-forming mechanism.     

Barium isotopes in allende meteorite: evidence against an extinct superheavy element

Carbon and chromite fractions from the Allende meteorite that contain isotopically anomalous xenon-131 to xenon-136 (carbonaceous chondrite fission or CCF xenon) at up to 5 x 10(11) atoms per gram show no detectable isotopic anomalies in barium-130 to barium-138. This rules out the possibility that the CCF xenon was formed by in situ fission of an extinct superheavy element. Apparently the CCF xenon and its carbonaceous carrier are relics from stellar nucleosynthesis.     

Chondrules in apollo 14 samples: implications for the origin of chondritic meteorites

Chondrules have been observed in several breccia samples returned by the Apollo 14 mission. These lunar chondrules are believed to have formed during a large impact event, perhaps the one that formed the Imbrian Basin. This suggests that some meteoritic chondrules are also formed by impact processes such as crystallization after shock melting and abrasion and diffusion in base-surge and fall-back deposits generated by impacts on planetary surfaces.     

Denver meteorite: a new fall

A meteorite, a single stone weighing 230 grams, was discovered in the roof of a warehouse on 17 July 1967; evidently it fell during the preceding week. The warehouse is on the northeast edge of Denver, Colorado; coordinates, 39 degrees 46'57'N, 104 degrees 55'50'W. This is the first recovered fresh fall in the United States since the Bells (Texas) meteorite of 9 September 1961. The composition and structure are those of an olivine-hypersthene chondrite.     

Farmington meteorite: cristobalite xenoliths and blackening

The Farmington chondrite contains two small xenoliths of granular cristobalite, each surrounded by a thin reaction rim of diopsidic clinopyroxene. Similarities between the blackened structure and drusy cavities, characteristic of this meteorite, and those of an experimentally heat-treated chondrite suggest that Farmington was reheated rather than shocked, but neither the exact stage in the history of this stone at which reaction rims developed around the xenoliths nor the source of the calcium necessary to form rim diopside have been established with certainty.     

Pyroxene-garnet transformation in coorara meteorite

Majorite is a new garnet in a veinlet of the Coorara meteorite. Its chemical composition is compatible with derivation mostly from original pyroxene, not from olivine as originally reported. Silicon is partly in sixfold coordination. Ringwoodite, a spinel of olivine composition, occurs as purple grains set in a matrix of fine-grained garnet. The similar mineralogy and texture of the Coorara and Tenham meteorites suggest a common parent body.     

Olivine-garnet transformation in a meteorite

Garnet has been identified for the first time as a meteorite mineral in the Coorara chondrite from Western Australia. It replaces olivine grains in a 1-millimeter veinlet traversing the body of the meteorite. The associated olivine has abnormally low birefringence, which suggests a highly shocked condition. Microprobe analyses do not distinguish the garnet from the associated olivine, which has the composition (Mg(.75)Fe(.25))(2) SiO(4); the garnet may have the composition Mg(3)Fe(2)Si(3)O(12) but be unresolvable from the accompanying olivine, or alternatively is nonstoichiometric. Transformation of olivine to garnet under high pressure could have significant implications for the phase composition of the Earth's mantle.     

Netschaevo: a new class of chondritic meteorite

The ratios of refractory elements to silicon and of zinc to silicon indicate that the silicate portion of the Netscha?vo meteorite is an ordinary chondrite. The scarcity of chondrules, the large dimensions (about 100 micrometers) of plagioclase grains, and the low indium content (0.09 nanogram per gram) indicate that Netscha?vo belongs to petrologic type 6. On a diagram of reduced iron versus oxidized iron, Netscha?vo lies along an extrapolation of the LL-L-H ordinary chondrite fractionation trend. The abundances of siderophile elements (nickel, germanium, iridium, and gold) are about 1.6 to 2.0 times greater than in H-group chondrites, and siderophile/nickel ratios are, with one exception, those expected from LL-L-H trends. This evidence indicates that Netscha?vo is an extremely iron-rich member of the ordinary chondrite sequence, and that plausible models to account for the ordinary chondrite sequence must produce materials having iron/silicon ratios 25 percent greater than those in CI carbonaceous chondrites. The existence of Netscha?vo emphasizes that the chondritic meteorites in terrestrial collections are a biased and incomplete selection of primitive solar system materials.     

Graphitic carbon in the Allende meteorite: a microstructural study

High-resolution transmission electron microscopy, shows that carbon in the Allende carbonaceous chondrite meteorite is predominantly a poorly crystalline graphite. Such material is of interest as an important carrier of the isotopically anomalous noble gases found in carbonaceous chondrites.     

Allende meteorite: a high-voltage electron petrographic study

Electron-transparent sections of the Allende meteorite, a carbonaceous chondrite, have been prepared by ion-thinning and examined by high-voltage (800-kilovolt) transmission electron microscopy. The matrix crystals, mainly olivine, range in size from approximately 5 to approximately 0.01 micrometers; carbon is present as intergranular films of poorly crystalline graphite. The chondrules exhibit extensive radiation damage, a feature lacking in the matrix. In addition, both chondrules and matrix are undeformed and contain negative crystals; submicroscopic exsolution lamellae are present in pyroxenes. Comparison of the substructure in the Allende meteorite with that in the Parnallee meteorite and in lunar and selected terrestrial rocks leads to the conclusion that chondrule irradiation preceded cold accretion during formation of the solar system and that the meteorite has since been undisturbed.     

Aromatic hydrocarbons in the murchison meteorite

Polynuclear aromatic hydrocarbons in the Murchison meteorite have been identified by the combined techniques of gas chromatography and mass spectrometry. The distribution of the aromatic compounds suggests that they are the products of a high-temperature synthesis.