Calcite Samples Research Articles

Distribution and Composition of Sulfide Minerals at Balmat, New York

Distribution and Composition of Sulfide Minerals at Balmat, New York

Exemple de gisements plombo-zinciferes epigenetiques dans des niveaux calcaires de sillon subsident; les mineralizations du Diois et des Baronnies

Abstract The mineralization of Diois and Baronnies (France) is examined on the individual specimen, bed, and regional levels. The mineral composition consists essentially of zinc blende, galena and pyrite with some marcasite in a calcitic gangue. Study of galena and calcite samples indicates a low temperature of deposition. Three phases of mineral concentration are hypothesized; precipitation of water-dissolved metallic ions by hydrosulfuric acid; upper Eocene deposition of lead and zinc concentrations along faults by ground water; and upper Miocene to Recent superficial alteration of the beds.

AN INVESTIGATION OF THE INTERCEPT METHOD FOR DETERMINING THE PROPORTION OF DOLOMITE AND CALCITE IN MIXTURES OF THE TWO: II. Experimental rates of solution of dolomite and calcite in samples consisting of a number of crystals

Experimental results are presented which support conclusions derived from a theoretical analysis of the log V vs. t plot, representing the rate of solution of dolomite consisting of a number of crystals. Experimentally determined rates of solution of dolomite and calcite are presented. The intercept method for determining the proportion of dolomite and calcite in mixtures of the two is evaluated on the basis of the theoretical and experimental results.

An X-Ray examination of a sample of pure calcite and of solid-solution effects in some natural calcites

In the course of the routine X-ray examination of a number of lowgrade iron ores in order to determine their constitution, it was observed that the calcite phase had varying interplanar spacings. Since these variations could have been due to differing solid-solution contents of other carbonates, further consideration was given to this point. The existence of these generally small amounts of solid solution is of some technological interest.A sample of 'specpure' calcite, supplied by Messrs. Johnson, Matthey & Co. Ltd., was used to provide accurate lattice parameters and interplanar spacings for pure calcite.

Physical and Chemical Properties of Ellenburger Rocks, Llano County, Texas

Physical and chemical data are recorded for 75 samples from a stratigraphic section of the Ellenburger group on Riley Mountain, Llano County, Texas. The division of samples is as follows: limestone, 29; dolomite, 42; mixed rocks, 4; a cherty limestone, a dolomitic limestone, and two calcitic dolomite samples. The limestone has a dense to sublithographic texture with pellet and breccia structures as variations. The average insoluble content of the limestone is 2.4 per cent; the minimum calcite content, about 94 per cent; and the maximum calculated dolomite content, about 3 per cent. The average grain density of 16 samples is 2.705; the average porosity of 12 samples is 0.5 per cent. Samples of the dolomite exhibit a range in texture and are classified in four groups: (1) micro-granular and very fine-grained; (2) fine-grained; (3) medium-grained; and (4) coarse-grained. Physical and chemical properties are more variable than those of the limestone samples, with ranges as follows: grain density, 2.811 to 2.848; porosity, 1.1 to 12.6 per cent; insoluble content, 0.2 to 10.2 per cent; calculated calcite content, 2.7 to 27.2 per cent; and calculated dolomite content, 70.0 to 94.7 per cent. Detrital minerals in the insoluble residues from the limestone and dolomite samples are quartz, feldspar, leucoxene, magnetite-ilmenite, tourmaline, zircon, muscovite, garnet, and apatite. Authigenic minerals include chert, quartz, feldspar, clay minerals, glauconite, and pyrite. Chert is the chief constituent of the residues, and varieties are dense or cryptocrystalline, fine to coarsely granular, and fibrous chalcedonic. The dense and coarse-grained cherts are complementary, one to the other, in their distribution. The chert, particularly of the dolomite, commonly is dolomoldic, as are also granular kaolin and glauconite. Siliceous oolites and fragments of siliceous spicules occur in a few residues. In appearance and in bulk composition the limestone samples are remarkably uniform throughout the stratigraphic section. The dolomitic limestone and the calcitic dolomite samples come from a zone which marks the transition from the dolomitic to the calcitic facies of the Staendebach member of the Tanyard formation. The coarse-grained dolomite is restricted to the lower part of the Tanyard, and the microgranular and very fine-grained dolomite is limited to the Gorman and Honeycut formations. The residues from the Tanyard formation are characterized by dense chert; whereas the residues from the Gorman and Honeycut contain abundant detrital material, principally quartz and feldspar, in addition to chert. Five detailed chemical analyses of the Ellenburger limestone and dolomite are given, and a method for determining the approximate composition of samples based on determinations of grain density and insoluble content is described. The data are presented in tables and graphically.

Exploratory Study of Plural X-Ray Reflection Methods Applied to the Problem of the Diffraction Pattern of Calcite

An exploration of the possibilities and difficulties in the study of the x-ray diffraction patterns of crystals with the method of the plural reflection spectrometer is described. This method, first suggested to the present authors by P. Kirkpatrick, has been analyzed in a recent ${\mathrm{article}}^{1}$ by one of us and the present article describes our first attempts to apply these ideas and to refine and extend the suggested methods of the first article. Diffraction patterns of calcite samples for Mo $K\ensuremath{\alpha}$-radiation were studied with three nearly parallel crystal faces reflecting x-rays in (1,-1,1) order, Allison's notation, or {1,1,1} order, DuMond's notation, and it was found that the fillets to be expected as approaches on the sides of the Prins diffraction pattern offer a serious obstacle to the direct use of this simple method. Two methods of circumventing the fillet difficulty are proposed, but not tried. A third method more readily adaptable to the equipment at hand, involving the use of three crystals and five successive reflections, was tried with a fair measure of success. Four successive reflections occur between two nearly parallel adjacent faces of a pair of large calcites. By adjusting these two calcites 1.5 seconds of arc off parallel there is good reason to believe that a narrower "tool" beam with reduced fillets was prepared with which the "object" crystal diffraction pattern was then explored. The observed diffraction patterns for the two calcite object crystals studied are shown. No asymmetry of the top of the pattern could be observed with reproducible certainty but this is to be expected since the theoretical asymmetry for Mo $K\ensuremath{\alpha}$-radiation in the first order on calcite is very small. An extension of present methods to longer wave-lengths in the vacuum region could quite possibly reveal such asymmetrical pattern shapes for at longer wave-lengths the asymmetry is more marked and the pattern is several times broader.Our results make it appear very doubtful whether the ideal flat topped diffraction pattern of Prins really obtains at the wave-lengths we have studied, the indications being that the real diffraction pattern has a sharper peak.

Tests of the Validity of X-Ray Crystal Methods of Determininge

The procedure in determining the electronic charge, $e$, from measurements of x-ray diffraction angles and the density of crystals has been criticized on the ground that while the density measurements are averages of a large volume, say 10 cc of crystal, the x-rays are diffracted from a surface layer as determined by "extinction" only about 4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ cm thick, a very small fraction of the total volume in an entirely specialized location. Partial answers to this criticism by Y. C. Tu and by Allison and Armstrong have rendered its validity much less probable. The present work with extremely fine powdered calcite samples whose density was determined with a pycnometer closes the question completely, we believe, leaving no ground whatever for the criticism and placing the x-ray determinations of $e$ on a very solid experimental foundation. Our work yields a value for $e$ of 4.799\ifmmode\pm\else\textpm\fi{}0.007 abs. e.s.u. based on the scale of ruled grating wave-lengths in which Cu $K{\ensuremath{\alpha}}_{1}$ has a wave-length (Bearden's value) of 1.5406\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ cm. Efforts to remove the above objection by studies on macroscopic calcite samples which failed to withstand our own criticisms are described since they emphasize the pitfalls that a conclusive test must avoid. Several new unexplained crystal diffraction effects discovered in this search for a conclusive test are also described. Agreement to one part in six thousand between Bragg and Laue diffraction angles was established for two different sets of Miller indices in macroscopic calcite.

The Disposition of Work Energy Applied to Crystals

The experiments described in this paper were initiated for the purely practical purpose of securing data to be used for an energy balance of the process of comminution of solids. The technologic problem is not considered here but rather the antecedent fundamental and scientific one of attempting to describe the thermodynamic properties of crystals as a function of particle size. It has been customary to ascribe observable variations in the properties of crystalline materials of large or fine particle size to a change of free energy, entropy or heat content resultant from the subdivision. Consideration of the first law of thermodynamics with reference to the application of work energy to crystals allows for only two obvious possibilities: (1) The heat produced in the crystals by the applied work is equal to it, whence no change of intrinsic energy of the material can occur; or (2) part only of the work appears as heat and the intrinsic energy of the crystals must increase. In this latter case, it is supposed that the energy corresponding to the increase of intrinsic energy is ``stored'' in the surficial layers of the crystal particles. We shall offer no apology for approaching the problem of testing these alternatives in a strictly empirical manner and for presenting data which may seem to contradict much of previous theory and experiment concerning the ``surface energy'' of solids. However tempting a review and criticism of previous attempts to measure or theoretically define this quantity might be, the elementary approach represented by our work now seems essential for understanding of the anomalous results, both of ourselves and others. Experimental test based on the first law, as expressed above, obviously could be either by (1) attempting to determine the change of intrinsic energy of fine compared to coarse particles of suitable materials or (2) by comparing the work and heat during the comminution process. Both of these experimental alternatives are described below. Thus we shall first describe experiments upon the heat of solution of fine and coarse calcite, designed to reveal measurable differences of intrinsic energy due to comminution. Further, we have investigated the specific heat at low temperatures of similar samples of calcite, and later of finely drawn wires of copper and aluminum in the annealed compared to the cold-worked state, referring to that part of the intrinsic energy represented by heat content. Finally, in the case of copper and aluminum, we have adopted the second experimental alternative of comparing the work and heat during a drawing process.

Reflection of Positive Ions by Crystals

FURTHER experiments on the reflection of hydrogen positive rays from crystals, similar to those described in NATURE for Jan. 11, have shown that the phenomenon is more complex than might have been expected. More than a hundred photographs showing reflected rays have been obtained under various conditions, and they show several features of interest. Great differences have been found in the reflecting powers of different samples of calcite. Two were found that gave strong reflected rays when the glancing angle was less than two degrees. The images obtained on Schumann plates placed at right angles to the beam may be properly termed reflection patterns, as they show considerable complexity, vary in a regular manner with the angle of incidence, and can be reproduced at will with the same setting of the crystal and speed of the rays. Six other calcite crystals gave reflection patterns containing fewer lines or lines on a fogged background. Reflected rays were also observed with a diamond which was kindly loaned by Dr. D. Cooksey. A natural cleavage face of this diamond had been used in experiments on the reflection of gamma rays. A highly polished face gave indistinct patterns on a fogged background. Clear lines were obtained from two other faces, one of which was the natural cleavage face, and the other a face that had been cut and appeared rough, due to saw marks. No reflected rays were found in a few trials with rock salt, galena, and magnetite.

Reflection of Positive Ions by Crystals

FURTHER experiments on the reflection of hydrogen positive rays from crystals, similar to those described in NATURE for Jan. 11, have shown that the phenomenon is more complex than might have been expected. More than a hundred photographs showing reflected rays have been obtained under various conditions, and they show several features of interest. Great differences have been found in the reflecting powers of different samples of calcite. Two were found that gave strong reflected rays when the glancing angle was less than two degrees. The images obtained on Schumann plates placed at right angles to the beam may be properly termed reflection patterns, as they show considerable complexity, vary in a regular manner with the angle of incidence, and can be reproduced at will with the same setting of the crystal and speed of the rays. Six other calcite crystals gave reflection patterns containing fewer lines or lines on a fogged background. Reflected rays were also observed with a diamond which was kindly loaned by Dr. D. Cooksey. A natural cleavage face of this diamond had been used in experiments on the reflection of gamma rays. A highly polished face gave indistinct patterns on a fogged background. Clear lines were obtained from two other faces, one of which was the natural cleavage face, and the other a face that had been cut and appeared rough, due to saw marks. No reflected rays were found in a few trials with rock salt, galena, and magnetite.