THE RUHOBOBO,RWANDA METEORITE: A NEW L6 CHONDRITE

Ruhobobo is a new meteorite which fell in Rwanda, Africa, in 1976. We found and analyzed olivine (Fa 23.4), opx (Fs 19.7, Wo 1.4), cpx (Fs 7.5, Wo 44.0), plagioclase (An 11.7, Or 5.6), chromite, “whitlockite”, kamacite, taenite and troilite. Based on these analyses and on microscopic observation, Ruhobobo is an unshocked L6 chondrite.     

THE TOULON METEORITE: A NEW CHONDRITE FROM ILLINOIS

Toulon is an olivine-bronzite chondrite found near Toulon, Illinois in 1962. It contains abundant, well preserved chondrules, as well as glasses that are not well devitrified. Most of the metal has been weathered out. Olivine and pyroxene are well equilibrated. We have classified it as an H5 chondrite.     

THE IJOPEGA CHONDRITE: A NEW H6 FALL

The Ijopega (Papua New Guinea) meteorite is a new H6 group chondrite fall which contains olivine (Fa 19.9 mole %), bronzite (Fs 17.8 mole %), plagioclase (An 12.1 Or 6.3 Ab 81.6 mole %), diopside, kamacite, taenite, troilite, chromite and whitlockite. The meteorite is extensively recrystallized and brecciated, and shows evidence of moderate shock deformation. Examination of Fe²⁺ and Mg partitioning between ortho- and clinopyroxene indicates a high equilibration temperature (940° or 880 °C). Chemical analysis shows the meteorite to be rich in S, containing about twice the average H-group abundance. Trace elements, including REE, are in accord with established H-group chondrite abundances.     

A NEW OLIVINE-BRONZITE CHONDRITE FROM DE KALB,MISSOURI

In the spring of 1969, an olivine-bronzite chondrite weighing approximately 575 g was found within the city limits of De Kalb, Missouri. Though the discovery site is only 3 miles west of the known area of Faucett meteorites, “De Kalb” is shown in this paper to represent a distinct fall     

CILIMUS: A NEW CHONDRITE FALL

Cilimus is a new Indonesian chondrite. Its mineralogy and chemistry categorize it as a veined, intermediate-to-white hypersthene or L-5 chondrite. Black veins and impact-produced glasses including maskelynite show evidence that Cilimus has been severely shocked.     

THE KRAMER CREEK,COLORADO METEORITE: A NEW L4 CHONDRITE

The Kramer Creek, Colorado, chondrite was found in 1966 and identified as a meteorite in 1972. Bulk chemical analysis, particularly the total iron content (20.36%) and the ratio of Fe_total/SiO₂ (0.52), as well as the compositions of olivine (Fa_21.7) and orthopyroxene (Fs_18.3) place the meteorite into the L-group of chondrites. The well-defined chondritic texture of the meteorite, the presence of igneous glass in the chondrules and of low-Ca clinopyroxene, as well as the slight variations in FeO contents of olivine (2.4% MD) and orthopyroxene (5.6% MD) indicate that the chondrite belongs to the type 4 petrologic class.     

THE MARYVILLE METEORITE: A 1983 FALL OF AN L6 CHONDRITE

The Maryville chondrite fell on January 28, 1983 in eastern Tennessee. Compositions of olivine (Fa 24.5), orthopyroxene (Fs 20.8), plagioclase (An 10.6), along with the bulk composition and siderophile concentrations, indicate L-group classification. The presence of highly equilibrated minerals, strongly recrystallized matrix, and the development of large, clear plagioclase grains suggest petrologic type 6 classification. Subsequent to metamorphism the meteorite was subjected to high transient pressures that converted some feldspar to glass, deformed the silicates, and caused small amounts of melting to occur. The effects of this shock event correspond to shock facies “d” or “e”.     

RAGLAND,AN LL3.4 CHONDRITE FIND FROM NEW MEXICO

The Ragland, New Mexico chondrite was found in 1978, and consists of a single stone of 12.16 kg that broke into three pieces. The stone is moderately weathered and has a pronounced chondritic texture. Bulk composition favors an LL classification, and modal analysis and oxygen isotopic composition are consistent with this. The thermoluminescence sensitivity of 0.056 ± 0.020 normalized to Dhajala, compositional variability of olivine (mean Fa 18.3, σ = 10.1) and low-Ca pyroxene (mean Fs 14.6, σ = 6.7), and Ca concentrations in olivine indicate metamorphic subtype 3.4 ± 0.1. The isotopically heavy oxygen composition, which is characteristic of subtypes 3.0–3.1, may be a primary characteristic and not a result of weathering. Low concentrations of radiogenic ⁴⁰Ar and planetary ³⁶Ar suggest noble gas loss.     

THE MILLS,NEW MEXICO,CHONDRITE — A NEW FIND

A mineralogical and chemical analysis has been performed on a slice of the Mills, New Mexico, chondrite, which was found in August 1970. The mineralogical composition is olivine Fa_19.5, bronzite, Fs_17.4, plagioclase, nickel-iron, troilite and ilmenite. The chemical analysis confirms that Mills is a typical bronzite, H5 chondrite, with considerable degree of weathering, as indicated by the presence of large amounts of Fe₂O₃. A comparison with other stones found in the same New Mexico region by Nininger may show a possible relation between Mills and previous finds.     

HAMMOND DOWNS,A NEW CHONDRITE FROM THE TENHAM AREA,QUEENSLAND, AUSTRALIA

Among a collection of meteorites from the area of the Tenham shower (Queensland, Australia) was a 27 kg stone which proved to be different from the other Tenham stones. It is a bronzite, H4, chondrite, the principal minerals being olivine (average composition Fa _18.8), clinobronzite and bronzite (average composition Fs_16.4), nickel-iron, and troilite; it is considerably weathered, much of the nickel-iron being converted to limonite. It has a highly chondritic structure, with devitrified glass within the chondrules, and without visible plagioclase. This meteorite was found about 1950 near the Hammond Downs station, hence the name; its coordinates are lat 25° 28′ S., long 142° 48′ E.     

THE NARAGH METEORITE: A NEW OLIVINE-BRONZITE CHONDRITE FALL

At 9:20 A.M. on August 18, 1974, a stony meteorite of approximately 3200 grams struck the roof of a secondary school at Naragh, Central Iran, (51°30′E, 33°45′N). The ellipsoidal dark-gray meteorite was 17 × 15 × 13 cm (density 3.62 gr/cm³). XRF and wet chemical analysis yields the bulk composition of the meteorite as follows in weight percent: Fe 11.95, Ni 1.05, Co 0.07, FeS 5.49, SiO₂ 37.15, TiO₂ 0.15, Al₂O₃ 2.43, Cr₂O₃0.62, FeO 14.25, MnO 0.23, MgO 23.79, CaO 1.61, Na₂O 0.92, K₂O 0.08, P₂O₅ 0.26. Modal mineral contents (in volume percent) are olivine 40, orthopyroxene 25, clinopyroxene 3, plagioclase 10.5, chromite 0.80, phosphate 0.70, troilite 6, metal phases 14. The meteorite is fine-grained, with average grain size about 0.4–0.6 mm and contains numerous recrystallized glassy chondrules. Olivine occurs as laths and radiating crystals in chondrules and as coarse-grained phenocrysts and interstitial microcrystalline grains in the matrix. These olivines have relatively uniform composition (Fo_80–82Fa_20–18). Fine-grained skeletal orthopyroxenes of average composition (En₁₆Fs₈₂Wo₀₁) are inter-grown with olivine in both chondrules and matrix. Clinopyroxene and plagioclase of average composition (En_6.5Fs₄₈Wo_45.5) and (Ab₈₂An₁₂Or₀₆) respectively, are evenly distributed in the matrix, together with kamacite (Fe_92–95), plessite (Fe_69.6–82.2) and taenite (Fe_46.7–66.1), troilite (Ni-free) and chromite grains. The high ratios of total Fe to SiO₂ of 0.71, metallic Fe to total Fe of 0.54, and SiO₂ to MgO of 1.56 in the bulk composition, the Fa component of olivine grains of 17.5–19.6, and the high Ca content of orthopyroxenes between 0.53 and 0.87 wt % suggest that the Naragh meteorite belongs to the H-group and petrologic type 6 of Van Schmus and Wood (1967) classification. In addition, the occurrence of fine-grained clear sodic plagioclase, the presence of numerous recrystallized chondrules with homogeneous silicate minerals, and the absence of Ni in the sulfide phase indicate that the Naragh meteorite has been metamorphosed after the initial crystallization in the parental body.     

THE BEAVER-HARRISON,BEAVER COUNTY,UTAH L6 CHONDRITE

The Beaver-Harrison, Utah chondrite (find July 24, 1979), a single, shock-veined stone of 925 grams, consists of major olivine (Fa_25.0), low-Ca pyroxene (En_77.3Fs_21.1Wo_1.6) and metallic nickel-iron; minor troilite and plagioclase (Ab_82.6An_11.1Or_6.3), accessory high-Ca pyroxene (En_47.0Fs_8.5Wo_44.5), chromite (Cm_8.7Sp_10.6Uv_9.4Pc_0.6Hc_0.7), chlorapatite and whitlockite; and hydrous ferric oxide of terrestrial weathering origin. Mineral compositions indicate L-group classification, and homogeneity of minerals, highly recrystallized texture and presence of clear plagioclase suggest that the meteorite belongs to petrologic type 6.     

AN L6 CHONDRITE FOUND NEAR PARACHILNA,SOUTH AUSTRALIA*

An 8.82 kg stony meteorite found on Motpena Station, 31°6' S, 138° 16' E, near Parachilna, South Australia, is shown to be a somewhat weathered L6 (olivine-hypersthene) chondrite. This is listed in The Meteoritical Bulletin, No. 53, June 1975 as MOTPENA, Synonym, Parachilna.     

AN H4–6 CHONDRITE: MOTTA DI CONTI

The mineralogical and chemical compositions of meteorites from the Motta di Conti, Vercelli, Italy, shower (February 29, 1868) have been determined. Microprobe analyses, of olivine (Fa_19,6) and orthopyroxene (Fs_17,8), as well as the bulk chemical composition, particularly the ratios of SiO₂/MgO (1.50), Fe°/Ni° (11.03), Fe_total/SiO₂ (0.81), Fe°/Fe_total (0.70) and the content of Fe_total (28.60%) classify the meteorite as an H-group chondrite. The percentage of total metallic nickel-iron (22.06%) is somewhat higher than the average in H-group chondrites. The texture of our stone shows evidence of metamorphism. The integration between matrix and chondrules is advanced and may suggest a high petrographic grade, but the identification of several microscopic features (e.g. small grains of monoclinic twinned pyroxene, FeNi-FeS intergrowths, globules and mosaic) leads to the conclusion that a variety of petrographic types (4–6) are present. Metamorphic equilibration in chondrites is discussed and a preliminary hypothesis for H4–6 chondrites is suggested.     

GOBABEB,A NEW CHONDRITE: THE COEXISTENCE OF EQUILIBRATED SILICATES AND UNEQUILIBRATED SPINELS

Gobabeb, an ordinary chondrite, was found near Gobabeb, South West Africa in 1969. Chemically and petrographically it belongs in the H4 group. But, in addition to almost homogeneous silicates and chromites, it contains rare, non-opaque spinels that vary greatly in composition from grain to grain. A similar association in an “almost equilibrated” portion of the Mezö-Madaras chondrite has been interpreted as evidence against the hypothesized metamorphic homogenization of ordinary chondrites. A comparison of the chromites and variable spinels from Mezö-Madaras and Gobabeb suggests, instead, that cation exchange is simply slower in the variable spinels than in the chromites. Based on the evidence to date, the survival of these highly variable spinels is not incompatible with a metamorphic episode for both these meteorites.     

THE CORREO AND SUWANEE SPRING METEORITES: TWO NEW ORDINARY CHONDRITE FINDS

Two new ordinary chondrites were found about 40 km west of Albuquerque, New Mexico. Correo is an H4 chondrite with distinct chondrules and major olivine (Fo_81.4), orthopyroxene (En_82.3) and plagioclase (An₁₂). Suwanee Spring is an L5 chondrite with few distinct chondrules and a highly recrystallized matrix. Major minerals are olivine (Fo_75.4), orthopyroxene (En_77.7) and plagioclase (An₉). The metallic Ni-Fe phases of both meteorites are typical of slowly-cooled ordinary chondrites.     

RICA AVENTURA: A NEW IRON METEORITE FROM CHILE

Rica Aventura, a group IVA fine octahedrite, was found in 1910 near the now abandoned village of Rica Aventura, Chile (69° 37′W, 21° 59′S). Based on chemical evidence it appears to be a unique new find.