The Effect of Gypsum Plaster on The Dry Rate of Emulsion

This study was carried out to access the effect of gypsum plaster on the dry rate of emulsion paint. Gypsum plaster sourced from paint manufactures was added in presence of other raw materials to archive a better formulation. The pH the present product (8.4) falls within standard value of paints .The viscosity of the archived was 10 poise compared to that of standard products (8 poise). The dry time however recorded was 70 minutes compared to that of standard product which is usually 90 -110 minutes. These results underscore the need to further explore the use of gypsum plaster in the manufacture of paints considering its positive effects on the properties of paint especially in the reduction of the dry rate. These results underscore the need to further explore the use of gypsum plaster in the manufacture of paints considering its positive effects on the properties of paint especially in the reduction of the dry rate. Keywords: dry rate

Controlling morphology using low molar mass nucleators

This chapter focuses on the use of low molar mass compounds which self-assemble in to fibrillar structures within a polymer melt. Application of modest shear rate to the system will result in a common alignment of these fibrils which can serve as row nuclei for the subsequent crystallisation of the polymer matrix. Thus the combination of small quantities of a low molar mass compound and modest shear flow leads to a semi-crystalline morphology with a well defined anisotropy and morphology

Processing a Locally Sourced Gypsum Material for Medical and Industrial Applications

Gypsum is a favourite when it comes to mimicking certain features of human body and enhancing some properties of industrial products made from it. Gypsum is widely used for medical purposes such as design of dental prosthetics and limbs support in orthopaedics; but the gypsum powder used for these products are usually well processed. Gypsum ore samples were obtained from a mine at Ibese in Ogun State, Nigeria and processed in a multistage de-gritting operation to obtain a grit-free powder which was converted to gypsum plaster (Plaster of Paris, POP) at about 220oC. The plaster powder so produced was used with property enhancing additives like calcium carbonate, sodium chloride, warm water and others to produce some medical and industrial products. Some of the medical products were tested at the State Specialist Hospital Ado-Ekiti and were found to conform with the required standard for such applications in medicine (especially dentistry and orthopedic). Other products such as chalk and wallboards were also produced from the processed gypsum and these also performed satisfactorily. Results of property tests showed that the products will have long service life.Keywords— multistage processing, de-gritting, property enhancer, dewatering, durability, dental, orthopaedics.

Precise and accurate isotope fractionation factors (α17O, α18O and αD) for water and CaSO4·2H2O (gypsum)

Gypsum (CaSO4·2H2O) is a hydrated mineral containing crystallization water, also known as gypsum hydration water (GHW). We determined isotope fractionation factors (α17O, α18O and αD) between GHW and free water of the mother solution in the temperature range from 3 °C to 55 °C at different salinities and precipitation rates. The hydrogen isotope fractionation factor (αDgypsum-water) increases by 0.0001 units per °C between 3 °C and 55 °C and salinities <150 g/L of NaCl. The αDgypsum-water is 0.9812 ± 0.0007 at 20 °C, which is in good agreement with previous estimates of 0.981 ± 0.001 at the same temperature. The α18Ogypsum-water slightly decreases with temperature by 0.00001 per °C, which is not significant over much of the temperature range considered for paleoclimate applications. Between 3 °C and 55 °C, α18Ogypsum-water averages 1.0035 ± 0.0002. This value is more precise than that reported previously (e.g. 1.0041 ± 0.0004 at 25 °C) and lower than the commonly accepted value of 1.004. We found that NaCl concentrations below 150 g/L do not significantly affect α18Ogypsum-water, but αDgypsum-water increases linearly with NaCl concentrations even at relatively low salinities, suggesting a salt correction is necessary for gypsum formed from brines. Unlike oxygen isotopes, the αDgypsum-water is affected by kinetic effects that increase with gypsum precipitation rate. As expected, the relationship of the fractionation factors for 17O and 18O follows the theoretical mass-dependent fractionation on Earth (θ = 0.529 ± 0.001). We provide specific examples of the importance of using the revised fractionation factors when calculating the isotopic composition of the fluids

THE STONE BOOK

The aesthetic value of a wild and/or tourist cave is well known everywhere. Anyway, presently only few people are aware that caves are the most important natural laboratories, in which it is possible to complete studies and researches that, in some cases, would be impossible in any other place. The caves are normally characterized by low energy and by the absence, or at least scarcity, of perturbing factors characterizing the external environments. Therefore, natural cavities may be regarded as perfect accumulation traps, preserving all the materials falling inside them. In the last half century the importance of cave deposits grew enormously in the field of paleoenvironmental and paleoclimatological studies, often allowing to reconstruct the chronology of the events a given environment underwent. From this point of view speleothems are by far the most important cave deposits, because their layered structure is always chronologically ordered and several techniques allow for an easy absolute dating of even a single event. Moreover, all these events may sometimes be restricted to a single year interval (or even less) on the basis of the speleothem growth layers. The speleothem’s layered structure makes reasonable to consider each of them a “stone book”, where each growing layer corresponds to a “page” of a multidisciplinary encyclopaedia. We are still unable to extract most of the information recorded by them. But in the near future, when we will be able to read all the pages of these “stone books”, their scientific importance will grow exponentially

Precise and accurate isotope fractionation factors (α17^{17}O, α18^{18}O and αD) for water and CaSO4_{4}·2H2_{2}O (gypsum)

Gypsum (CaSO$_{4}$·2H$_{2}$O) is a hydrated mineral containing crystallization water, also known as gypsum hydration water (GHW). We determined isotope fractionation factors (α$^{17}$O, α$^{18}$O and αD) between GHW and free water of the mother solution in the temperature range from 3 °C to 55 °C at different salinities and precipitation rates. The hydrogen isotope fractionation factor (αD$_{gypsum-water}$) increases by 0.0001 units per °C between 3 °C and 55 °C and salinities <150 g/L of NaCl. The αD$_{gypsum-water}$ is 0.9812 ± 0.0007 at 20 °C, which is in good agreement with previous estimates of 0.981 ± 0.001 at the same temperature. The α$^{18}$O$_{gypsum-water}$ slightly decreases with temperature by 0.00001 per °C, which is not significant over much of the temperature range considered for paleoclimate applications. Between 3 °C and 55 °C, α$^{18}$O$_{gypsum-water}$ averages 1.0035 ± 0.0002. This value is more precise than that reported previously (e.g. 1.0041 ± 0.0004 at 25 °C) and lower than the commonly accepted value of 1.004. We found that NaCl concentrations below 150 g/L do not significantly affect α$^{18}$O$_{gypsum-water}$, but αDgypsum-water increases linearly with NaCl concentrations even at relatively low salinities, suggesting a salt correction is necessary for gypsum formed from brines. Unlike oxygen isotopes, the αD$_{gypsum-water}$ is affected by kinetic effects that increase with gypsum precipitation rate. As expected, the relationship of the fractionation factors for $^{17}$O and$^{18}$8O follows the theoretical mass-dependent fractionation on Earth ($\textit{θ}$ = 0.529 ± 0.001). We provide specific examples of the importance of using the revised fractionation factors when calculating the isotopic composition of the fluids.This research was supported by the ERC WIHM Project [#339694] to DAH

Three study cases of growth morphology in minerals: Halite, calcite and gypsum

AbstractBeyond fundamental aspects of crystal growth and morphology, the growth of minerals is a challenging subject because in most cases we face a problem with unknown growth conditions. Actually, in the field of geological studies, we have to decipher the growth conditions of a crystal using the information contained in the very crystal. One of these characteristics of crystals that contain information about their growth is their morphology and time evolution. In this article, we introduce the subject of crystal morphology by using three important minerals, calcite, halite and gypsum, as three didactic case studies to illustrate the application of the current knowledge in the field

Fluid inclusion study of gypsum precipitated in acid saline waters: Salar Ignorado, northern Chile

Salar Ignorado is situated at high elevation in the Andes Mountains of northern Chile in an extremely arid, small, intervolcanic basin and contains pools of acid (pH 3.3 -- 4.1) saline (5 -- 30 ppth) water that are precipitating gypsum crystals. Gypsum crystals trap acid saline water from the pools as fluid inclusions. Little research has been conducted on fluid inclusions in gypsum. At Salar Ignorado two types of bottom-growth gypsum form from the surface pools: large bladed and tiny needle-like crystals. Salar Ignorado gypsum contains primary fluid inclusions of three distinct morphologies, oriented parallel to crystal face. Petrography and microthermometry were performed on 27 gypsum crystals from Salar Ignorado. Most primary fluid inclusions are all liquid, however some primary inclusions are composed of liquid and a gas phase. One large gypsum crystal, hosting primary fluid inclusions along 28 successive growth bands, was the focus for fluid inclusion studies. Microthermometric results in geochemical trends. This crystal shows a change in parent fluids, during growth, from low salinity to high salinity to low salinity. At the bottom of the crystal, the lowest six fluid inclusion assemblages have salinities of 1.7 to 5.1 eq. wt. % NaCl. The next nine fluid inclusion assemblages have significantly higher salinity (18.6 and 25.5 eq. wt. % NaCl) inclusions. The twelve fluid inclusion assemblages near the top of the crystal have low salinity (1.6 to 7.9 eq. wt. % NaCl) like those at the bottom of the crystal. The high salinity fluid inclusions in the middle of this gypsum crystal are interpreted as the migration of hydrothermal fluids to the surface, which are intimately linked to the local active magmatism. Secondary evidence of hydrothermal pulses are high molecular weight hydrocarbons and hydrogen sulfide odors upon crushing.;A variety of microorganisms are trapped both as solid inclusions and as potentially viable halophilic and acidophilic prokaryotes and eukaryotes within fluid inclusions in this Mars-analog gypsum. Pennate diatoms, green algae, and prokaryotes have been documented in gypsum precipitated from acid (pH 1.8--4.6) saline (5%--28% total dissolved solids) waters at Salar Ignorado and its larger neighbor, Salar Gorbea. Evaluation of Salar Ignorado gypsum indicates that primary fluid inclusions record hydrochemistry and microbiology of various intervals of waters. This study has implications for detailed interpretations of past environments from ancient gypsum in the rock record, as well as clues for the search for life on Mars.;This thesis has shown for the first time that primary fluid inclusions in gypsum can serve as proxies for various environmental conditions. Detailed study of Salar Ignorado gypsum has identified trends in surface water salinity, degassing of hydrogen sulfide and hydrocarbons, and fossilization of microorganisms

Formation of natural gypsum megacrystals in Naica, Mexico

Contains 4 figures.Exploration in the Naica mine (Chihuahua, Mexico) recently unveiled several caves containing giant, faceted, and transparent single crystals of gypsum (CaSO4•2H2O) as long as 11 m. These large crystals form at very low supersaturation. The problem is to explain how proper geochemical conditions can be sustained for a long time without large fluctuations that would trigger substantial nucleation. Fluid inclusion analyses show that the crystals grew from low-salinity solutions at a temperature of ~54 °C, slightly below the one at which the solubility of anhydrite equals that of gypsum. Sulfur and oxygen isotopic compositions of gypsum crystals are compatible with growth from solutions resulting from dissolution of anhydrite previously precipitated during late hydrothermal mineralization, suggesting that these megacrystals formed by a self-feeding mechanism driven by a solution-mediated, anhydrite-gypsum phase transition. Nucleation kinetics calculations based on laboratory data show that this mechanism can account for the formation of these giant crystals, yet only when operating within the very narrow range of temperature identified by our fluid inclusion study. These singular conditions create a mineral wonderland, a site of scientific interest, and an extraordinary phenomenon worthy of preservation.We gratefully acknowledge Compañía Peñoles for the facilities provided during the field studies performed in the Naica mine, and the Ministerio de Educación y Ciencia of Spain for financial support.Peer reviewe