Fluorite Grains Research Articles

Diagenetic fluorite in chalks from Stevns Klint and Møns Klint, Denmark

Small quantities of fluorite occur as sand- and silt-sized material in a Cretaceous/Tertiary chalk-marl-limestone sequence at Stevns Klint and in a Lower Maastrichtian Chalk sequence at Møns Klint, Denmark. The habit of the fluorite is either hexahedral or irregular. The fluorite grains enclose calcite particles that commonly have a parallel optical orientation. On the basis of morphology and inclusions, it is suggested that the fluorite is diagenetic, having formed by replacement of skeletal grains.

Studies of the reaction of crystalline calcium carbonate with aqueous solutions of NH 4F, KF and NaF

The reaction between solid calcium carbonate and the aqueous fluorides NH 4F, KF, and NaF has been completely investigated. The reaction of CaCO 3 (solid) is completely independent of the dimensions of its polycrystalline particles and gives calcium fluoride. The calcium fluoride is formed in the same form and size as the grains of the original calcium carbonate. A course crystalline fluorite is formed at a satisfactory rate and with a sufficiently high mechanical strength to be of industrial interest. The course of the reaction appears to involve penetration of the fluoride solution into the body of a grain through voids which develop in the solid material owing to the formation of polycrystalline CaF 2 with a different molar volume as compared with CaCO 3. Data were obtained on the rate of formation and nature of the fluoride formed. The fluorite which is formed around the dissolving calcite was shown by X-ray diffraction and electron microscopy to have a polycrystalline aggregated structure and an estimate is made of crystallite size. The fluorite grains are pseudomorphs of the calcite crystals and there is crystallographic orientation of the product with respect to the parent phase.

浮選における粒子に作用する支持力について

The suspension of particles in froth flotation is classified into two types, one of which is by air bubbles in the pulp, and the other is by liquid film in the froth layer. The formulae of supporting force in both cases were investigated and verified by some experiments.The results obtained are as follows:(1) On the supporting force in the pulp, Momosaki's equation was confirmed by the correlation of contact angle to the maximum supporting angle by the experiments on some cylindrical samples and different solutions. Results of the skin flotation on the sized fluorite grains also verified the above conclusion.(2) An equation was proposed as the supporting force in the froth layer tor the large cylindrical sample, neglecting the thickness of liquid film. f=2πd·T·sinΘ where f: supporting force, d: diameter of cylinder, T: surface tension, Θ: supporting angle.This equation was found to be correct on the basis of the results of the experiments obtained on cylindrical samples. The maximum supporting force did not relate to the contact angle, due to the fact that the maximum supporting angle was always obtained at 90°.(3) The floating experiments, using 0.5g/l sodium oleate solution and sized sample of quartz (contact angle=0°), and fluorite (35°), in the froth layer, also proved the item (2). For very fine particles (-200 mesh), however, the effect of contact angle appeared and spraying of solution (the increase of film thickness) helped this tendency.

The bedding-replacement fluorspar deposits of Spar Valley, Eagle Mountains, Hudspeth County, Texas

The Spar Valley fluorspar district in the Eagle Mountains, Hudspeth County, Texas, is one of the few in the western United States containing bedding-replacement fluorspar deposits. The deposits at Spar Valley resemble the bedding-replacement deposits of the Cave in Rock fluorspar district of southern Illinois. Two distinct deposits, the North and the South ore bodies, are present. The North ore body is larger and has been developed by diamond drilling and mining; the following statements apply chiefly to it.The fluorspar partly replaces a sequence of three sandy limestones interbedded with four calcareous shales in the lower part of the Edwards limestone of Lower Cretaceous age. The fluoritized beds, which dip 40 degrees SW in conformity with underlying limestone, are overlain by thick impermeable gouge along a bedding-plane fault dipping slightly more than 40 degrees SW. The high-grade beds were derived from the sandy limestones, and the low-grade beds, which contain as much as 28 percent of CaF 2 , were formed from the calcareous shales. The selectiveness of replacement by the fluorine-bearing solutions, due to differences in the chemical composition, texture, and degree of brecciation of the original rock, resulted in bedding-replacement deposits of variable fluorite content.A reduction in volume, which accompanied the replacement, led to the development of many cavities. During the later stages of fluoritization these cavities were lined with fluorite crystals, early fluorite grains were coated and interstices between them were filled, and fluorite veins were formed in the ore beds and the underlying dense limestone.