Mutual Interference in the Microchemical Determination of Ore Minerals

The use of microchemical methods is spreading rapidly, both for the qualitative and quantitative determination of elements. Microchemistry offers a decided advantage over "bulk" methods, not only because of the greater speed with which the determinations can be carried out, but also because of the very small amounts of material required for a test. Microchemical methods are particularly valuable in determining the composition of the small inclusions in ores and metallurgical products. Most of the reagents used are sufficiently sensitive to show the presence of 0.005 per cent or less of the desired element. Needless to say, if such minute quantities of an element are to be identified, it is essential that the procedure of the test be carefully followed and the utmost caution taken that there is no pollution of the reagent or the test drop. Despite such care, it frequently happens that the test obtained is not wholly satisfactory. Either the color of the precipitate is unusual, the form is changed or entirely different, or sometimes no test is obtained when previous observations have indicated that the element should be present. When such changes occur-and they occur frequently, even in the hands of skilled technicians-the observer is never certain whether they are due to variations in the PH of the solution, concentration of reagent or solution, or to the presence of some interfering anion or cation. The first two variables can be controlled by proper attention to the procedure of the test; in many cases the last variable-presence of an interfering anion or cation-is beyond control. Often, much time could be saved by recognizing that a given variation in the precipitate is caused by the presence of another element. In fact, some of the interferences are as characteristic of the interfering element as any other known test. The presence of a variety of elements in the test drop is due either to a poor sample or to a complex mineral. A poor sample is obtained if the original area of the mineral or inclusion is too small. In this case, allowance can usually be made for the presence in the solution of elements of the host mineral, although their presence may cause notable interferences. Where the mineral varies in composition there may be no hint of the presence of elements, other than those expected in the mineral, until trouble is encountered in the testing.</p

Magnetometer Examination of the Monte Cristo Magnetite-Ilmenite Deposits

Situated in the San Gabriel Mountains of Southern California is a large body of anorthosite which is associated a number of bodies of ilmenitic magnetite. During the summer of 1937, the E. I. duPont de Nemours Corporation obtained options on a group of properties thought to contain several such deposits. In connection with the exploration of the aforementioned deposits, the authors were employed as geophysicists to conduct a magnetic examination of the area. The data contained in this report was collected between August 9 and September 4, 1937. Mr. Dawson is, at the present time, continuing the magnetometer investigation and, in the light of the facts to be presented in the following pages, his work is being watched with considerable interest

The Geochemistry of Quicksilver Mineralization. Magnetometer Examination of the Monte Cristo Magnetite-Ilmenite Deposits

The geochemistry of quicksilver mineralization: The investigation has involved a geochemical, petrographic, and spectographic study of quicksilver mineralization. It has been found that cinnabar can be deposited only from alkaline sulphide ion concentration which is, in turn, partially dependent on the alkalinity of the solution. Such alkaline solutions are capable of dissolving silica, but carbonate and alkaline earth ions cannot exist together in such alkaline solutions. Any carbonatization of quicksilver deposits must thus represent a stage in the period of mineralization distinct from the period of cinnabar deposition. However, silica is often deposited syngenetically with cinnabar and the relationship of cinnabar and silica (unlike that of cinnabar and carbonate) is so intimate that the cinnabar occurs, in some places, as an extremely fine dispersion throughout associated silica. Associated with quicksilver mineralizing solutions are small amounts of a number of heavy metals as iron, chromium, manganese, arsenic, antimony, gold, silver, copper, zinc, nickel, germanium, lead, and cobalt. Of these elements, copper, silver, cobalt, lead, and germanium are always differentially concentrated in the cinnabar and such differential concentrations as have been observed are independent of the geographical and geological location of the deposit and are likewise independent of the type of wall rock in which the deposit occurs. The varying shades of cinnabar coloration cannot be attributed to any spectrographically determinable concentrations of any elements nor to the total amount of impurity which is differentially concentrated in the cinnabar. The cinnabar-bearing solutions gain access into the wall rocks through fractures and intergranular voids and the greater part of all cinnabar ores is the result of such open-space filling. When the openings become filled, however, the solutions are quite capable of replacing the adjacent wall rock. If the wall rock is out of equilibrium with the quicksilver mineralizing solutions, the adjustment of equilibrium and consequent precipitation of mercuric sulphide will be quite rapid. Precipitation of cinnabar is caused primarily by relief of pressure, evaporation of solvent, and wall rock reaction. Except in ammoniacal solutions, a decrease in temperature will not cause precipitation. Dilution of solutions causes the precipitation of metacinnabar and colloidal mercury. Such dilution is probably responsible for the native mercury which is a common, minor component of many quicksilver deposits. Acidification will likewise precipitate metacinnabar, but not cinnabar. The infrequent occurrences of metacinnabar can best be explained by near-surface dilution or acidification of hypogene solutions. Insofar as temperature and alkalinity are concerned, pyrite or both pyrite and marcasite could be formed simultaneously with cinnabar of metacinnabar or both. However, where marcasite occurs with cinnabar alone (as is quite commonly the case), the marcasite has probably been deposited separately form the cinnabar. Since cinnabar (rather than metacinnabar) is deposited only from hot alkaline solutions and since oxidized mercury minerals are very rare, supergene deposition of cinnabar must be a very local and a very uncommon occurrence. Some cinnabar darkens rapidly on exposure to sunlight and it is suggested that this darkening may involve the formation of a surficial layer of colloidal mercury in solid solution in the cinnabar. Magnetometer examination of the Monte Cristo magnetite-ilmenite deposits: Situated in the San Gabriel Mountains of Southern California is a large body of anorthosite which is associated a number of bodies of ilmenitic magnetite. During the summer of 1937, the E. I. duPont de Nemours Corporation obtained options on a group of properties thought to contain several such deposits. In connection with the exploration of the aforementioned deposits, the authors were employed as geophysicists to conduct a magnetic examination of the area. The data contained in this report was collected between August 9 and September 4, 1937. Mr. Dawson is, at the present time, continuing the magnetometer investigation and, in the light of the facts to be presented in the following pages, his work is being watched with considerable interest. </p

Magnetometer traverses in the Monte Cristo area: Supplement 1 from "Magnetometer examination of the Monte Cristo magnetite-ilmenite deposits" (Thesis)

Situated in the San Gabriel Mountains of Southern California is a large body of anorthosite which is associated a number of bodies of ilmenitic magnetite. During the summer of 1937, the E. I. duPont de Nemours Corporation obtained options on a group of properties thought to contain several such deposits. In connection with the exploration of the aforementioned deposits, the authors were employed as geophysicists to conduct a magnetic examination of the area. The data contained in this report was collected between August 9 and September 4, 1937. Mr. Dawson is, at the present time, continuing the magnetometer investigation and, in the light of the facts to be presented in the following pages, his work is being watched with considerable interest

Observation of burst activity from SGR1935+2154 associated to first galactic FRB with H.E.S.S.

Fast radio bursts (FRB) are enigmatic powerful single radio pulses with durations of several milliseconds and high brightness temperatures suggesting coherent emission mechanism. For the time being a number of extragalactic FRBs have been detected in the high-frequency radio band including repeating ones. The most plausible explanation for these phenomena is magnetar hyperflares. The first observational evidence of this scenario was obtained in April 2020 when an FRB was detected from the direction of the Galactic magnetar and soft gamma repeater SGR1935+2154. The FRB was preceded with a number of soft gamma-ray bursts observed by Swift-BAT satellite, which triggered the follow-up program of the H.E.S.S. imaging atmospheric Cherenkov telescopes (IACTs). H.E.S.S. has observed SGR1935+2154 over a 2 hour window few hours prior to the FRB detection by STARE2 and CHIME. The observations overlapped with other X-ray bursts from the magnetar detected by INTEGRAL and Swift-BAT, thus providing first observations of a magnetar in a flaring state in the very-high energy domain. We present the analysis of these observations, discuss the obtained results and prospects of the H.E.S.S. follow-up program for soft gamma repeaters and anomalous X-ray pulsars

Deep observations of Kepler's SNR with H.E.S.S.

Kepler’s supernova remnant (SNR) which is produced by the most recent naked-eye supernova in our Galaxy is one of the best studied SNRs, but its gamma-ray detection has eluded us so far. Observations with modern imaging atmospheric Cherenkov telescopes (IACT) have enlarged the knowledge about nearby SNRs with ages younger than 500 years by establishing Cassiopeia A and Tycho’s SNRs as very high energy (VHE) gamma-ray sources and setting a lower limit on the distance to Kepler’s SNR. This SNR is significantly more distant than the other two and expected to be one of the faintest gamma-ray sources within reach of the IACT arrays of this generation. We report strong evidence for a VHE signal from Kepler’s SNR based on deep observations of the High Energy Stereoscopic System (H.E.S.S.) with an exposure of 152 hours, including 122 hours accumulated in 2017-2020. We further discuss implications of this result for cosmic-ray acceleration in young SNRs

Observation of burst activity from SGR1935+2154 associated to first galactic FRB with H.E.S.S.

Fast radio bursts (FRB) are enigmatic powerful single radio pulses with durations of several milliseconds and high brightness temperatures suggesting coherent emission mechanism. For the time being a number of extragalactic FRBs have been detected in the high-frequency radio band including repeating ones. The most plausible explanation for these phenomena is magnetar hyperflares. The first observational evidence of this scenario was obtained in April 2020 when an FRB was detected from the direction of the Galactic magnetar and soft gamma repeater SGR1935+2154. The FRB was preceded with a number of soft gamma-ray bursts observed by Swift-BAT satellite, which triggered the follow-up program of the H.E.S.S. imaging atmospheric Cherenkov telescopes (IACTs). H.E.S.S. has observed SGR1935+2154 over a 2 hour window few hours prior to the FRB detection by STARE2 and CHIME. The observations overlapped with other X-ray bursts from the magnetar detected by INTEGRAL and Swift-BAT, thus providing first observations of a magnetar in a flaring state in the very-high energy domain. We present the analysis of these observations, discuss the obtained results and prospects of the H.E.S.S. follow-up program for soft gamma repeaters and anomalous X-ray pulsars

The young massive stellar cluster Westerlund 1 in gamma rays as seen with H.E.S.S.

Massive stellar clusters have recently been hypothesised as candidates for the acceleration of hadronic cosmic rays up to PeV energies. Previously, the H.E.S.S. Collaboration has reported about very extended $\gamma$-ray emission around Westerlund 1, a massive young stellar cluster in the Milky Way. In this contribution we present an updated analysis that employs a new analysis technique and is based on a much larger data set, allowing us to constrain better the morphology and the energy spectrum of the emission. The analysis technique used is a three-dimensional likelihood analysis, which is especially well suited for largely extended sources. The origin of the $\gamma$-ray emission will be discussed in light of multi-wavelength observations