Supergene Enrichment of Silver Ores with Special Reference to those from Neihart, Montana.

In the development of a technique it was necessary to learn the fundamentals of ore microscopy as applied to the various minerals of silver, which included the use of reflected polarized light, etch reactions, micro­chemical analysis, and sight recognition of mineral. In addition it was necessary to become familiar with the accepted criteria of sequence, replacement, and other textural phenomena.

Microscopic Study of Montana Silver Ores.

A microscopic investigation of the Montana silver minerals was conducted. This study consisted mainly of identifying the silver and silver-bearing minerals and of determining their paragenetic rela­tionships. The increasing amount of research in which the reflecting microscope is employed is evidence of the great value of this method of approach in the solution of problems of paragenesis of the opaque minerals.

A Metallurgical Study of Gold Ores

Gold is widely distributed in the earth's crust in small quantities. Gold is found in nature in two forms; the element itself and the compound gold telluride. In all cases, silver in some proportion is an alloying constituent.

A Study and Application of the Process of Supergene Enrichment of Silver Ores.

In many deposits of silver ores the grade of the ore de­creases considerably a few hundred feet below the surface. It is believed that in many cases the better ores owe their richness in part to the process of sulphide enrichment. It is recognized, however, that many rich silver ores are hypogene deposits that have been affected very little, if any, by processes of enrichment.

The Inhibitory Effects of Carbonaceous Materials on the Cyaniding of Gold Ores.

Carbon and carbonaceous material have been known to have a deleterious effect upon the cyanidation of gold and silver ores since the very beginning of the process. Organic matter is a common source of impu­rities in cyanide solution, its reducing effect being notorious.

The Presence of Rhenium in Montana Manganese Ores.

Rhenium properties offer many interesting possibilities, therefore any ores containing rhenium would be of considerable value. Its close relationship to manganese in the periodic table led to the belief that manganese ores would be an excellent place to search for the metal. Investigation of the literature of rhenium revealed that no ore was known to contain more than 0.001 per cent of rhenium.

An Investigation of the Ores of the Big Seven Mine, Neihart, Montana

During the course of this investigation of the ores of the Big Seven mine, Neihart, Montana, the writer has attempted, through a mi­croscopic study of polished sections, to ascertain the hypogene or supergene character of the ore minerals present in the ore suite.

Corrosion Testing of Iron-Tin Alloys by the Salt Spray Method

The purpose of this study was to determine the rela­tive rate of corrosion of iron-tin alloys containing low percentages of tin. Since in the world today, a great deal of work is being done to develop large tin deposits and new methods devised to treat these ores, it is possible that the metal will become abundant and will obtain a more important position in the metal industry.

Sēfer ʿEṣ ḥayyîm : doz izṭ ein daiṭš ḥummāš zammṭ hafṭores und 5 megiles miṭ der algmein berihmṭen daiṭšen iberzetzung

[Moses Mendelssohn]

Description and chemical and mineral composition of iron oxide samples from two Finnish lakes

Fifteen iron oxide accumulations from the bottoms of two Finnish lakes ("lake ores") were found to contain as much as 50% Fe. Differential X-ray powder diffraction and selective dissolution by oxalate showed that the samples consisted of poorly crystallized goethite and ferrihydrite. The crust ores of one lake had higher ferrihydrite to goethite ratios than the nodular ores of the other lake. The higher ferrihydrite proportion was attributed to a higher rate of Fe2+ supply from the ground water and/or a higher rate of oxidation as a function of water depth and bottom-sediment permeability. Values of Al-for-Fe substitution of the goethites determined from unit-cell dimensions agreed with those obtained from chemical extraction if the unit-cell volume rather than the c dimension was used. In very small goethite crystals a slight expansion of the a unit-cell dimension is probaby compensated by a corresponding contraction of the c dimension, so that a contraction of the c dimension need not necessarily be caused by Al substitution. The goethites of the two lakes differed significantly in their Al-for-Fe substitutions and hence in their unit-cell sizes, OH-bending characteristics, dehydroxylation temperatures, dissolution kinetics, and Mössbauer parameters. The difference in Al substitution (0 vs. 7 mole %) is attributed to the Al-supplying power of the bottom sediments: the silty-clayey sediments in one lake appear to have supplied A1 during goethite formation, whereas the gravelly-sandy sediments in the other lake did not. The compositions of the goethites thus reflect their environments of formation.

Chemical composition of hydrothermal sulfide minerals from the Rainbow, Logachev-1, and Logachev-2 hydrothermal fields

Composition of ore minerals in MAR sulflde occurrences related to ultramaflc rocks was studied using methods of mineragraphy, electron microscopy, microprobe analysis, and X-ray analysis. Objects are located at various levels of maturity of sulflde mounds owing to differences in age, duration and degree of activity of the following hydrothermal systems: generally inactive Logatchev-1 field (up to 66.5 ka old), inactive Logatchev-2 field (3.9 ka), and generally active Rainbow field (up to 23 ka). Relative to MAR submarine ore occurrences in the basalt substrate, mineralization in the hydrothermal fields mentioned above is characterized by high contents of Au, Cd, Co, and Ni, along with presence of accessory minerals of Co and Ni. The studied mounds differ in quantitative ratios of major minerals and structural-textural features of ores that suggest their transformation. Ores in the Logatchev-1 field are characterized by the highest Cu content and development of a wide range of multistage contrast exsolution structures of isocubanite and bornite. In the Logatchev-2 field, sphalerite-chalcopyrite and gold-arsenic exsolution structures are present, but isocubanite exsolution structures are less diverse and contrast. The Rainbow field is marked by presence of homogenous isocubanite and the subordinate development of exsolution structures. The authors have identified four new phases in the Cu-Fe-S system. Phases X and Y (close to chalcopyrite and isocubanite, respectively) make up lamellae among isocubanite exsolution products in the Logatchev-1 and Logatchev-2 fields. Phase Y includes homogenous zones in zonal chimneys of the Rainbow field. Phases A and B formed in the orange bornite domain at low-temperature alteration of chalcopyrite in the Logatchev-1 field. Mineral assemblages of the Cu-S system are most abundant and diverse in the Logatchev-1 field, but their development is minimal in the Logatchev-2 field where mainly Cu-poor sulfides of the geerite-covellite series have been identified. Specific features of mineral assemblages mentioned above reflect the maturity grade of sulfide mounds and can serve as indicators of maturity.