Through The Sandglass: Uses. Anyone walking on the beach or through the dunes will often notice areas of dark gray smeared across the surface, often outlining ripples, as if an artist had highlighted the sand's topography with charcoal. I encountered many examples of such designs recently at the dunes of Kelso (above) and Oceano, and on California's beaches. Look closely, and you'll see that these patterns are characterised by concentrations of dark grains, gathered together in a much higher proportion than elsewhere in the sand. Look even more closely, down a microscope, and there they are, little black nuggets nestling among the glittering quartz grains (the example below is from Kelso).
As my messing around with kitchen physics showed, sand, like all granular materials, dislikes being mixed and will find endless ways of sorting itself out into its components. Slightly less easily moved. With time, the lighter grains are winnowed out and the heavier ones left, concentrated. Résultats Google Recherche d'images correspondant à. PAGE D'ACCUEIL MATEL Group. ALMA SOTAPHARM - Transformation m canique de tubes de verre. Verre online :: Dossiers thématiques - Fours et fusion. Ellipse Labo. CERAVERRE: Travail du Verre au chalumeau. VIO Tubes Borosilicates.