X-ray powder diffraction
This handout provides background on the use and theory of X-ray powder diffraction. Examples of applications of this method to geologic studies are provided.
Information Handout↗
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TSX-PLUS MULTI-TASKING UPGRADE FOR THE NICOLET L-11 POWDER DIFFRACTION SYSTEM.
In August of 1982, a single-user, dual-translator, automated powder diffraction system was purchased by the Denver Research Institute for use on project work in the Chemical and Materials Sciences Division. Within a short period of time, the system had already become saturated with users. Scheduling conflicts arose. In view of these problems, an answer was sought in the form of hardware and software changes which would allow many users access to the system simultaneously. A low-cost, minimum impact solution was eventually found. The elements of the solution are reported.
Conference Paper↗
Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane
Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.
Canadian Journal of Physics↗
Effect of chlorine in clay-mineral specimens prepared on silver metal-membrane mounts for X-ray powder diffraction analysis
Silver metal-membrane filters are commonly used as substrates in the preparation of oriented clay-mineral specimens for X-ray powder diffraction (XRD). They are relatively unaffected by organic solvent treatments and specimens can be prepared rapidly. The filter mounts are adaptable to automatic sample changers, have few discrete reflections at higher 20 angles, and, because of the high atomic number of silver, produce a relatively low overall background compared with other membrane filters, such as cellulose (Poppe and Hathaway, 1979). The silver metal-membrane filters, however, present some problems after heat treatment if either the filters or the samples contain significant amounts of chlorine. At elevated temperature, the chloride ions react with the silver substrate to form crystalline compounds. These compounds change the mass-absorption coefficient of the sample, reducing peak intensities and areas and, therefore, complicating the semiquantitative estimation of clay minerals. A simple procedure that eliminates most of the chloride from a sample and the silver metal-membrane substrate is presented here.
Clays and Clay Minerals↗
Least-squares refinement of powder diffraction data for unit cell parameters: Program listing for DEC 10 computer
This FORTRAN computer program is a time-sharing version of the classic program of Appleman and Evans (1973) and Evans, Appleman, and Handwerker (1963), which indexes powder patterns and refines unit-cell dimensions. The program, originally written to be processed in batch mode for an IBM computer, was modified to run in time-sharing mode on the DEC 10 computer. This version does not depart philosophically from the original program; however, the input and output formats have been adapted to the time-sharing terminal. These modifications and the actual running of the program are not discussed in detail here, as this report is intended only to make the program itself available. Examples of the input and output formats are shown on pages 3-8. Input can be entered through the terminal by two methods. An input file may either be independently created and then entered into the program later, or created directly through the interactive mode of the program. With the latter method a file of the input information may also be saved for later use. Both methods allow for the data to be edited after each refinement run. The output format has been changed to an 80-column width, common to many terminals. Only the last refinement cycle is printed and some of the statistical computations have been surpressed. Using the "Unit Cell" program from the terminal in a "real time" situation emphasizes the versatility of the program. This ability to interact directly with the computer gives the user a better appreciation of the program, its options, the data, and the problem being solved.
Open-File Report↗
Hanawaltite, Hg1+6Hg2+[Cl,(OH)]2O3 - A new mineral from the Clear Creek claim, San Benito County, California: Description and crystal structure
Hanawaltite, ideally Hg 1+ 6 Hg 2+ O 3 Cl 2 , is orthorhombic, Pbma (57), with unit-cell parameters refined from powder data: a =11.790(3), b =13.881(4), c =6.450(2) Å, V =1055.7(6) Å 3 , a : b : c =0.8494:1:0.4647, Z =4. The strongest six lines of the X-ray powder-diffraction pattern [ d in Å ( I )( hkl )] are: 5.25 (80)(111), 3.164 (60)(231), 3.053 (100)(041), 2.954 (70)(141), 2.681 (50)(401), and 2.411 (50)(232,341). The mineral is an extremely rare constituent in a small prospect pit near the long-abandoned Clear Creek mercury mine, New Idria district, San Benito County, California. It was found on a single-fracture surface where it is intimately associated with calomel, native mercury, cinnabar, montroydite, and quartz. Individual crystals are subhedral to anhedral, platy to somewhat bladed, and average about 50 μm in longest dimension. The largest known crystal is approximately 0.3×0.3 mm in size and is striated parallel [001]. Hanawaltite is opaque to translucent (on very thin edges), black to very dark brown–black in color, with a black to dark red–brown streak. Other physical properties include: metallic luster; cleavage {001} good; uneven fracture; brittle; nonfluorescent; H <5; calculated density (for the empirical formula) 9.51 g/cm 3 . In polished section, hanawaltite is moderately to strongly bireflectant and is pleochroic white ( R I ) to blue–white ( R 2 ). In reflected plane-polarized light, it is white with orange–red internal reflections in very thin grains and at grain margins. The anisotropy is strong with bright metallic blue rotation tints. Measured reflectance values, in air and in oil, are tabulated. Electron-microprobe analysis yielded Hg 2 O 82.46, HgO 14.27, Cl 3.33, H 2 O [0.34], sum [100.40], less O=Cl 0.75, total [99.65] wt. %, corresponding to Hg 1+ 6.00 Hg 2+ 1.00 [Cl 1.43 (OH) 0.57 ] Σ2.00 O 3.00 , based on O+Cl=5. After the crystal structure was determined, the original microprobe value for Hg 2 O, 96.2, was partitioned in a ratio of 6Hg 2 O:HgO and (OH) was calculated, such that Cl+(OH)=2. The hanawaltite structure consists of undulatory [Hg–Hg] 2+ ribbons which roughly parallel (100). The diatomic [Hg–Hg] 2+ groups have anion tails which, in turn, serve as cross linkages between dimer ribbons through [Hg 2+ O 2 Cl 2 ] planar rhombs. The structure is compared to that of other mercury oxychlorides and each is found to have its own unique structural features. This structural diversity is attributed to the inherent ability of mercury to adopt either metallic or ionic types of bonds. The mineral name honors the late Dr. J. D. (Don) Hanawalt (1903–1987), who was a pioneer in the field of X-ray powder diffraction.
California↗
Additional studies on mixed uranyl oxide-hydroxide hydrate alteration products of uraninite from the palermo and ruggles granitic pegmatites, grafton county, New Hampshire
Additional studies on an incompletely characterized secondary uranium "mineral" from the Ruggles and Palermo granitic pegmatites, New Hampshire, referred to as mineral "A" by Frondel (1956), reveal a mixture of schoepite-group minerals and related uranyl oxide-hydroxide hydrated compounds. A composite chemical analysis yielded (in wt.%): PbO 4.85 (EMP), UO3 83.5 (EMP), BaO 0.675 (av. of EMP and ICP), CaO 0.167 (av. of EMP and ICP), K2O 2.455 (av. of EMP and ICP), SrO 0.21 (ICP), ThO2 0.85 (ICP), H2O 6.9, ??99.61. Powder-diffraction X-ray studies indicate a close resemblance in patterns between mineral "A" and several uranyl oxide-hydroxide hydrated minerals, including the schoepite family of minerals and UO2(OH)2. The powder-diffraction data for mineral "A" are most similar to those for synthetic UO2.86??1.5H2O and UO2(OH)2, but other phases are likely present as well. TGA analysis of both mineral "A" and metaschoepite show similar weight-loss and first derivative curves. The dominant losses are at 100??C, with secondary events at 400?? and 600??C. IR spectra show the presence of (OH) and H2O. Uraninite from both pegmatites, analyzed by LAM-ICP-MS, shows the presence of Th, Pb, K and Ca.
Canadian Mineralogist↗
Bobjonesite, V4+ O (SO4) (H2O)3, a new mineral species from Temple Mountain, Emery County, Utah, U.S.A
Bobjonesite, V 4+ O (SO 4 ) (H 2 O) 3 , is a new mineral species from Temple Mountain, Emery County, Utah, U.S.A. It occurs as blue-green crusts and efflorescences in fractures in a fossil (Triassic) tree; individual crystals are <<1 mm and are intimately intergrown. Bobjonesite hydrates very easily, and is unstable in all but the driest atmosphere. Its structure was determined on a crystal of bobjonesite; however, the physical properties, optical properties and X-ray powder-diffraction pattern were recorded on the synthetic equivalent, and an electron-microprobe analysis was not possible. Bobjonesite has a pale blue streak, a vitreous luster and no observable fluorescence under ultraviolet light. It has no cleavage or parting. The Mohs hardness is ~1, and the calculated density is 2.28 g/cm 3 . Bobjonesite is biaxial positive, with α 1.555(2), β 1.561(1), γ 1.574(2), 2 V (obs.) = 72(1)°, 2 V (calc.) = 69°; it is non-pleochroic, X = b , Y ≈ a , Z ∧ c ≈ 19° (in β obtuse). Bobjonesite is monoclinic, space group P 2 1 / n , cell dimensions from single-crystal data: a 7.3940(5), b 7.4111(3), c 12.0597(9) Å, β 106.55(1)°, V 633.5(1) Å 3 , Z = 4. The strongest seven lines in the X-ray powder-diffraction pattern [ d in Å( I )( hkl )] are as follows: 5.795(100)(002), 3.498(90)(112), 3.881(48)(1̅03), 5.408(37) (101), 4.571(20)(012), 6.962(11)(1̅01) and 6.254(11)(011). The chemical formula was derived from crystal-structure analysis; the end-member formula is V O (SO 4 ) (H 2 O) 3 . The crystal structure of bobjonesite was refined to an R index of 3.6% for 1105 observed (| F o | > 5> F ) reflections measured with an automated four-circle X-ray diffractometer using Mo K α X-radiation. There is one V site occupied by V 4+ and surrounded by three O atoms and three (H 2 O) groups in an octahedral arrangement, with one short vanadyl bond (1.577 Å), four similar equatorial bonds (<2.022 Å>), and one longer V–O bond (2.278 Å) trans to the vanadyl bond. The structure consists of isolated [V 4+ 2 O 2 (H 2 O) 6 (SO 4 ) 2 ] clusters linked by hydrogen bonds.
Utah↗
Laboratory manual: mineral X-ray diffraction data retrieval/plot computer program
The Mineral X-Ray Diffraction Data Retrieval/Plot Computer Program--XRDPLT (VanTrump and Hauff, 1976a) is used to retrieve and plot mineral X-ray diffraction data. The program operates on a file of mineral powder diffraction data (VanTrump and Hauff, 1976b) which contains two-theta or 'd' values, and intensities, chemical formula, mineral name, identification number, and mineral group code. XRDPLT is a machine-independent Fortran program which operates in time-sharing mode on a DEC System i0 computer and the Gerber plotter (Evenden, 1974). The program prompts the user to respond from a time-sharing terminal in a conversational format with the required input information. The program offers two major options: retrieval only; retrieval and plot. The first option retrieves mineral names, formulas, and groups from the file by identification number, by the mineral group code (a classification by chemistry or structure), or by searches based on the formula components. For example, it enables the user to search for minerals by major groups (i.e., feldspars, micas, amphiboles, oxides, phosphates, carbonates) by elemental composition (i.e., Fe, Cu, AI, Zn), or by a combination of these (i.e., all copper-bearing arsenates). The second option retrieves as the first, but also plots the retrieved 2-theta and intensity values as diagrammatic X-ray powder patterns on mylar sheets or overlays. These plots can be made using scale combinations compatible with chart recorder diffractograms and 114.59 mm powder camera films. The overlays are then used to separate or sieve out unrelated minerals until unknowns are matched and identified.
Open-File Report↗
Mineralogical applications of electron diffraction. 1. Theory and techniques
The small wavelengths used in electron-diffraction experiments and the thinness of the crystals necessary for the transmission of the electron beam combine to require a somewhat different diffraction geometry for the interpretation of electron-diffraction patterns than is used in the interpretation of X-ray diffraction patterns. This geometry, based on the reciprocal lattice concept and geometrical construction of Ewald, needed for the interpretation. of transmission electron-diffraction single-crystal patterns is here reviewed. Transmission electron-diffraction single-crystal patterns of two monoclinic substances, colemanite [CaB 3 O 3 (OH) 3 •H 2 O] and potassium chlorate (KC10 3 ), are examined and the .theory necessary for their interpretation is given in detail. The study of these patterns furnishes a basis for the interpretation of single-crystal patterns of materials belonging to any crystal system. It is shown that useful unit-cell data, accurate to a few tenths of a percent, can be obtained from the patterns of colemanite and KClO 3 . A method of evaluating unit-cell data from measurements of such single-crystal patterns is given. The transmission electron-diffraction powder pattern obtained from an oriented aggregate of thin crystals gives the same unit-cell data as are given by the electron-diffraction single-crystal pattern obtained from one crystal of the aggregate., A graphical method is given for precisely evaluating unit-cell constants from measurements of such a powder pattern.
Trace Elements Investigations↗
Aurorite, argentian todorokite, and hydrous silver-bearing lead manganese oxide
During a study of hypogene manganese minerals, three silver-bearing manganese oxides were identified in "black calcite" associated with silver ores at the Aurora mine (Treasure Hill), Hamilton, Nevada. Specifically these are: (1) argentian chalcophanite (aurorite) (Ag 2 Ba,Ca,Pb,-K 2 ,Cu,Mn (super +2) )Mn 3 (super +4) O 7 . 3H 2 O; (2) argentian todorokite (Ag 2 ,K 2 ,Ca,Ba,-Na 2 ,Cu,Pb)Mn 4 (super +4) O 9 . 5H 2 O; and (3) hydrous silver-bearing lead manganese oxide (Pb,Cu,Ba,Sb,Ag 2 ,Ca,K 2 )Mn 5 (super +4) O 11 . 5H 2 O. Based on the large concentration of silver in argentian chalcophanite (7.50% Ag 2 O) and the low zinc content (0.25% ZnO) this mineral is recognized as a new species and named "aurorite."Physical and optical properties, and chemical analyses of the three minerals are presented together with X-ray powder diffraction data for aurorite and argentian todorokite. All chemical analyses were done with the electron microprobe analyzer. Due to extremely small particle size and textural relations, no X-ray powder data were obtained for the hydrous silver-bearing lead manganese oxide. Associated minerals include cryptomelane, pyrolusite, birnessite(?), cerargyrite, native silver, quartz, and manganoan calcite. Although the general uniform dark color of the "black calcite" and apparent uniform distribution of the inclusions suggests contemporaneous formation, examination of polished sections at high magnifications shows a definite paragenetic sequence. Manganoan calcite is replaced by fine-grained intergrowths of cryptomelane, pyrolusite, birnessite(?), and cerargyrite. Native silver formed early and the silver-bearing manganese oxides formed late in the sequence; aurorite fills microfractures that cut through all other minerals.These three silver-bearing manganese oxides were recognized only at the Aurora mine, Hamilton, Nevada, although black calcite veins were studied from numerous areas in the western United States. The geologic features of silver-bearing black calcites are described by Hewett and Radtke in the preceding paper.
Nevada↗
X-ray powder data for uranium and thorium minerals
The U.S. Geological Survey has in preparation a comprehensive volume on the mineralogy of uranium and thorium. This work has been done as part of a continuing systematic survey of data on uranium and thorium minerals on behalf of the Division of Raw Materials, U.S. Atomic Energy Commission. Pending publication of this volume and in response to a widespread demand among workers in uranium and thorium mineralogy, the X-ray powder diffraction data for the known minerals that contain uranium or thorium as an essential constituent are presented here. The coverage is complete except for a few minerals for which there are no reliable data owing to lack of authentic specimens. With the exception of that for ianthinite, the new data either originated in the Geological Survey or in the Mineralogical Laboratory of Harvard University. Data from the literature or other sources were cross-checked against the files of standard patterns of these laboratories; the sources are indicated in the references. Data not accompanied by a reference were obtained from films in the Harvard Standard File and cross-checked as to the identity of the film with the Geological Survey's file. Minor differences can be expected in the d-spacings reported for the same specimens by different investigators because of the manner of preparation of the mount, the conditions of X-ray irradiation, and the method of photography and measurement of the film or chart. The Harvard and Geological Survey data all were obtained from films taken in 114-mm diameter cameras, using either ethyl cellulose and toluene or collodion spindle mounts and Straumanis-type film mounting. Unless otherwise indicated all patterns were taken with copper radiation (Kα 1.5418 A.) and nickel filter and data are given in Angstrom units. The d-spacings are not corrected for film shrinkage. The correction ordinarily is small and in general is less than either the variation in spacing arising from differences in experimental technique of different investigators, including the varying absorption of samples of different thickness and concentration, or the variation attending slight changes in the chemical composition of the mineral. Some uranium minerals give poor diffraction patterns. The best results are generally obtained by using relatively small diameter spindles and long exposures, with a take-off angle from teh X-ray tube of about 4°. It is sometimes advantageous to shield the film from fluorescence in the visible region excited by X-ray irradiation. Copper radiation is preferable. The patterns of a few uranium minerals are greatly impaired by heavy grinding of the sample. Light crushing of the coarse sample after mixing with about one-third its volume of coarsely powdered low-absorption glass is helpful. Many uranium minerals, such as the members of the torbernite group, readily lose zeolithic water or transform to lower hydrates at or near ordinary conditions of temperature and humidity and care should be taken to control this in the manner of preservation and preparation of the sample.
Trace Elements Investigations↗
Phase relations in the CuVS system
Phase relations in the system Cu-V-S were studied by using a sealedcapsule technique, reflected-light microscopy, X-ray powder diffraction and electron microprobe analysis. In the temperature range between 300 and 900 ??C, six vanadium sulfides exist in the V-S system. These are VS, V7S8, V3S4, V5S8, V3S5 and VS4. In the Cu-V-S system, three Cu-V sulfides are stable. Both Cu3VS4 (sulvanite) and CuV2S4 are cubic with a = 5.391 ?? 0.005 A ?? and a = 9.789 ?? 0.005 A ?? respectively, and the third has a composition Cu0.8V1.1S2. CuV2S4 forms equilibrium assemblages with all vanadium sulfides, which restricts their effects on the phase relations in the system to a small region. ?? 1986.
Journal of the Less-Common Metals↗
Phase relations in the system CuMoS
Phase relations in the system CuMoS were studied in the temperature range 500-1000 ??C by using the conventional sealed, evacuated glass capsule technique. Reflected-light microscopy, X-ray powder diffraction and electron microprobe analysis were used for phase characterization. The chevrel-type phase, CuxMo3S4, is stable above 600??C, and forms equilibrium assemblages with the cubic Cu2S solid solution, copper, molybdenum, Mo2S3 and MoS2. Its solid solution ranges from Cu1.50-2.00Mo3S4 at 700??C to Cu1.22-2.00Mo3S4 at 1000 ??C. ?? 1990.
Journal of the Less-Common Metals↗
Natural attenuation can lead to environmental resilience in mine environment
Four streams flowing in the Iglesiente and Arburese mine districts (SW Sardinia, Italy), exploited for zinc (Zn) and lead (Pb) extraction from sulphides and secondary non-sulphide mineralization (calamine ores), have been studied combining investigations from the macroscale (hydrologic tracer techniques) to the microscale (X-ray powder diffraction, scanning electron microscopy, X-ray absorption spectroscopy). In the investigated area, concerns arise from release of metals to water during weathering of ore minerals and mine-waste. Specifically, Zn is observed at extremely high concentrations (10s of mg/L or more) in waters in some of the investigated catchments. The results from synoptic sampling campaigns showed marked differences of Zn loads, from 6.3 kg/day (Rio San Giorgio) to 2000 kg/day (Rio Irvi). Moreover, natural attenuation of metals was found to occur i) through precipitation of Fe compounds (Fe oxy/hydroxides and “green rust”), ii) by means of the authigenic formation of metal sulphides promoted by microbial sulphate reduction, iii) by metal intake in roots and stems of plants ( Phragmites australis and Juncus acutus ) and by immobilization in the rhizosphere, and iv) by cyanobacterial biomineralization processes that lead to formation of Zn-rich phases (hydrozincite and amorphous Zn-silicate) The biologically mediated natural processes that lead to significant abatement and/or reduction of metal loads, are the response of environmental systems to perturbations caused from mine activities, and can be considered part of the resilience of the system itself. The aim of this study is to understand the effect of these processes on the evolution of the studied systems towards more stable and, likely, resilient conditions, e.g. by limiting metal mobility and favoring the improvement of the overall quality of water. The understanding of how ecosystems adapt and respond to contamination, and which chemical and physical factors control these natural biogeochemical barriers, can help to plan effective remediation actions.
Sardinia↗
Multiple physical properties of gas hydrate-bearing sediments recovered from Alaska North Slope 2018 Hydrate-01 Stratigraphic Test Well
Knowledge of the petrophysical and geomechanical properties of gas hydrate-bearing sediments is essential for predicting reservoir responses to gas production from gas hydrate reservoirs. In December 2018, Stratigraphic Test Well Hydrate-01 was drilled in the western part of the Prudhoe Bay Unit, Alaska North Slope, as part of the technical planning effort for a future long-term gas hydrate production test. Side-wall pressure coring was conducted to recover gas hydrate-bearing sediments from two reservoir sections named Unit B and Unit D. A total of 34 cores were successfully recovered during five runs of a wireline deployed pressure corer, and a total of 17 cores were preserved for advanced laboratory analysis. The samples were frozen inside the pressure core autoclave by liquid nitrogen while at high pressure before being removed and stored under liquid nitrogen at atmospheric pressure. High-resolution X-ray computed tomography showed the samples were high-quality, with undisturbed lithological layers. The Unit B and D sediments were categorized as sand or sandy silt with high hydrate saturation. Gas compositions suggest the hydrates formed with thermogenic and microbial mixed gases. Permeability tests and triaxial compression tests were conducted on the hydrate-bearing sediments. Low strengthening and high permeability at hydrate saturation S h > 80% were observed. There was a small permeability reduction during the triaxial compression tests owing to porosity loss with increasing effective stress in the highly permeable sandy sediment after hydrate dissociation. The apparent minimal changes in porosity and permeability during the tests were due to the low-clay content and low compressibility of the quartz sand grains in the recovered cores. X-ray powder diffraction and thermal conductivity analysis also suggested a high quartz content for the analyzed samples.
Alaska↗
Diatom influence on the production characteristics of hydrate-bearing sediments: Examples from Ulleung Basin, offshore South Korea
The Ulleung Basin Gas Hydrate field expeditions in 2007 (UBGH1) and 2010 (UBGH2) sought to assess the Basin's gas hydrate resource potential. Coring operations in both expeditions recovered evidence of gas hydrate, primarily as fracture-filling (or vein type) morphologies in mainly silt-sized, fine-grained sediment, but also as pore-occupying hydrate in the coarser-grained layers of interbedded sand and fine-grained systems. A commonality across many of these occurrences is the presence of diatoms in the fine-grained sediment. Here we tested fine-grained sediment (median grain size <12.5 μm) associated with hydrate occurrences at four UBGH2 sites (UBGH2-2-2, UBGH2-3, UBGH2-6 and UBGH2-11) to investigate potential impacts of diatoms on efforts to extract methane from hydrate, or to tap hydrocarbon reservoirs beneath hydrate-bearing sediment. Two key considerations are: the extent to which diatoms control sediment mechanical properties, and the extent to which pore-water freshening, which occurs as gas hydrate breaks down during resource extraction, alters the diatom control on sediment mechanical properties. We conducted experiments to measure sediment index properties, sedimentation behavior and compressibility to address these considerations. We relied on scanning electron microscope (SEM) imagery and X-ray powder diffraction (XRD) to characterize the sediment mineralogy. Our high-level findings are that at the ∼20–45% (by volume) diatom concentrations observed at these UBGH2 sites, sediment compressibility increases with diatom content, but diatoms only appear to increase porosity and permeability at the highest diatom concentration (∼45%). Our measurements suggest in situ compression indices of 0.35–0.55 and permeabilities on the order of 0.01milliDarcies (1 × 10 −17 m 2 ) can be anticipated at these sites. Importantly, these properties are not expected to vary significantly upon pore water freshening that accompanies gas hydrate dissociation during production.
East Sea, Ulleung Basin↗