Four formalisms are outl ined. Crystal f ield theory explains the color as well as the f luorescence in transit ion-metal-containing minerals such as azurite and ruby. The trap concept, as part of crystal f ield theory, explains the varying stabi l i ty of electron and hole color centers with respect to l ight or heat bleaching, as well as phenomena such as thermoluminescence. The molecular orb...

Time resolved data on the carbon isotopic composition of carbonate minerals and the sulfur isotopic composition or sulfate minerals show a strong negative correlation during the Cretaceous. Carbonate minerals are isotopically heavy during this period while sulfate minerals are isotopically light. The implication is that carbon is being transferred from the oxidized, carbonate reservoir to the r...

Huntingtin-like proteins make yeast sick (bottom). eriin et al., reporting on page 997, have developed the first yeast model for studying Huntington's disease. Yeast cannot undergo neurodegeneration, of course, but the simplicity and genetic manipulability of the system are already providing important mechanistic insights. The authors report that aggregation of a polypeptide with an expanded po...

Thermoluminescence (TL) studies of insulators, including crystals of minerals such as calcite, quartz or zircon, have resulted in the development of a wider range of applications in the fields of radiation dosimetry and archaeological and geological dating. Most conventional TL measurements are made by recording light emission during heating by means of broad-band optical filters and blue-sensi...

Over the past fifty years the mineralogy and crystal chemistry of the materials called asbestos have been refined leading to better identification through new and more sensitive techniques. The health aspects of the exposure to fibrous inorganic species are also equally well determined from the anatomical to the biochemical levels. Integrating the efforts of many researchers from a diversity of...

The design of a neural network is presented for the recognition of six kinds of minerals (chalcopyrite, chalcosine, covelline, bornite, pyrite, and energite) and to determine the percentage of these minerals from a digitized image of a rock sample. The input to the neural network corresponds to the histogram of the region of interest selected by the user from the image that it is desired to rec...

Nanomineralogy is the study of Earth and planetary materials at nano-scales, focused on characterizing nanofeatures (like inclusions, exsolution, zonation, coatings, pores) in minerals and revealing nanominerals and nanoparticles [1,2]. With advanced high-resolution analytical scanning electron microscopy, we are now capable to characterize solid materials in situ easier and faster down to nano...

Particles with nanometer dimensions (nanoparticles) are all around us. The finest particles of sand are blown by the wind over thousands of kilometers. The finest particles of soils are either eroded by the wind in extremely dry conditions or by water under wet conditions and deposited hundreds of kilometers or more from the origin. The air contains nanoparticles of carbon, ice, and oxides and ...

The importance of minerals in the diet of horses is well recognized by horse owners and equine nutritionists alike. The type and quantity of minerals required are very diverse and essential minerals include the major or macrominerals and the trace or microminerals. This discussion will be restricted to three macrominerals, sodium, potassium, and chloride (Na+, K+, Cl-), that are essential to th...

Fibrous minerals are common in nature but asbestiform minerals are rare. The unique mineralogical characteristic common to all the asbestos minerals is their morphologic form (or habit of crystallization) as polyfilamentous fiber bundles. The individual fibrils within the bundles have a tendency to be very long with a narrow range of diameters and grow with their long fiber axis in parallel ori...