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Geology topics

E.J. Dwornik

Publications and source records attributed to E.J. Dwornik.

14 recordsLinked to original sources
USGS2002

The detection of sulphur in contamination spots in electron probe X-ray microanalysis

Sulphur has been identified as one of the elements present in the contamination spot which forms under the electron beam in the microprobe. The presence of the sulphur results in a rapid change in intensity measurements causing a loss of observed intensity for elements other than sulphur. The source of sulphur has been traced at least in part to the Apiezon B diffusion pump oil. A comparative X-ray fluorescence study of the Apiezon B and Octoil diffusion pump oils showed substantial amounts of sulphur in the Apiezon B. The Octoil was relatively free of sulphur.

British Journal of Applied Physics↗
USGS1986

Kassite from the Diamond Jo quarry, Magnet Cove, Hot Spring County, Arkansas: The problem of cafetite and kassite

Small (<0.5 mm), brownish-pink platy rosettes and yellow spherules, in cavities in nepheline syenite at the Diamond Jo quarry, Magnet Cove, Hot Spring County, Arkansas, have been identified as kassite, CaTi 2 O 4 (OH) 2 , a mineral previously known only from the Kola Peninsula, USSR. The Magnet Cove kassite is orthorhombic, in space group Ammm, A2mm, A222 , or A2,22 , with unit-cell parameters a = 12.10, b = 31.65, c = 4.95 Å, and Z = 16; d calc = 3.28 g/cm 3 . Principal X-ray powder lines [ d in Å, ( I )] are 7.85(10), 3.26(7), 2.565(7), 1.910(8), 1.898(6). The X-ray powder and single-crystal data and density correspond to those reported by earlier workers for cafetite, (Ca,Mg)(Fe,Al) 2 Ti 4 O 12 ·4H 2 O, from Kola, but the chemical and physical properties correspond to those given in their description of kassite. These earlier workers may have intermixed samples during their X-ray study of kassite and cafetite.

Arkansas↗
USGS1974

Naturally occurring vapor-liquid-solid (VLS) Whisker growth of germanium sulfide

The first naturally occurring terrestrial example of vapor-liquid-solid (VLS) growth has been observed in condensates from gases released by burning coal in culm banks. Scanning electron microscopy, X-ray diffraction, and energy dispersive analysis indicate that the crystals consist of elongated rods (≈ 100 μm) of germanium sulfide capped by bulbs depleted in germanium.

Journal of Crystal Growth↗
USGS1970

Semimicro chemical and x-ray fluorescence analysis of lunar samples

Major and selected minor elements were determined in seven whole rock fragments, five portions of pulverized lunar rock, and the lunar soil. Three different rock types were represented: vesicular, fine-grained basaltic rocks; medium- to coarse-grained, vuggy gabbroic rocks; and breccia. The ranges (in percent) for the major constituents of the lunar samples are: SiO 2 , 38 to 42; Al 2 O 3 , 8 to 14; total iron as FeO, 15 to 20; MgO, 6 to 8; CaO, 10 to 12; Na 2 O, 0.5 to 1; K 2 O, 0.05 to 0.4; TiO 2 , 8 to 13; MnO, 0.2 to 0.3; and Cr 2 O 3 , 0.2 to 0.4. The high reducing capacity of the samples strongly suggests the presence of Ti(III).

Science↗
USGS1970

Lunar clinopyroxenes: Chemical composition, structural state, and texture

Single-crystal x-ray diffraction, microprobe, optical and electron optical examinations of clinopyroxenes from Apollo 11 lunar samples 10003, 10047, 10050, and 10084 show that generally the crystals are composed of (001) augite-pigeonite intergrowths in varying ratios. Transmission electron micrographs reveal abundant exsolution lamellae, many only 60 Å thick. In addition to the phase inhomogeneities, primary chemical inhomogeneities are clearly demonstrated. There are reciprocal relationships between calcium and iron and between Ti 4+ + 2Al and R 2+ + 2Si. Our evidence suggests that a chemically inhomogeneous subcalcic C 2/ c augite was the only primary pyroxene from which pigeonite later exsolved.

Science↗
USGS1966

Nickel-iron spherules from Aouelloul glass

Nickel-iron spherules, ranging from less than 0.2 to 50 microns in diameter and containing 1.7 to 9.0 percent Ni by weight, occur in glass associated with the Aouelloul crater. They occur in discrete bands of siliceous glass enriched in dissolved iron. Their discovery is significant tangible evidence that both crater and glass originated from terrestrial impact.

Aouelloul crater↗
USGS1963

Transformation of montmorillonite to kaolinite during weathering

Extensive deposits of kaolinite in Florida are formed by transformation of montmorillonite during low-temperature supergene weathering. The transformation occurs by intracrystalline leaching of interlayer cations and tetrahedral silica layers. Interposition of stripped layers within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, a new clay structure. Kaolin-like layers are nourished by lateral epitaxy, as the iron-rich montmorillonite decomposes. Hexagonal outgrowths of new kaolinite develop at the edges of montmorillonite flakes and nucleate new vertical growth. Kaolinitic sands impregnated with goethite are ultimately formed, and the released silica enriches groundwater and forms secondary chert.

Florida↗
USGS1962

Metallic spherules in tektites from Isabela, Philippine Islands

Iron-nickel spherules, as much as 0.5 mm in diameter, have been found completely embedded in some philippinites. The spherules consist mainly of kamacite with unidentified pink inclusions. The meteoritic origin of these spherules seems reasonable, suggesting that the tektites containing them were formed by asteroidal or meteoritic impact.

Isabela↗