Sub-aerial biofilms (SAB) are ubiquitous, self-sufficient microbial ecosystems found on mineral surfaces at all altitudes and latitudes. SABs, which are the principal causes of weathering on exposed terrestrial surfaces, are characterized by patchy growth dominated by associations of algae, cyanobacteria, fungi and heterotrophic bacteria. A recently developed in vitro system to study colonizati...

Macroand micro-perthitic microclines from pegmatites from Perth, Ontario (Wards catalogue 46 E 0510) and Keystone, South Dakota (Wards 46 E 5125) have been studied using light and electron microscopy. A sample of the type perthite from Perth, Ontario (Hunterian Museum, Glasgow, M2361) was compared using light microscopy. It differs in bulk composition and microtexture from the Wards sample. The...

Equations have been derived and computations carried out for the demineralization rates of tooth enamel employing the “Fluorapatite” model. The model assumes that when hydroxyapatite is exposed to a low fluoride concentration, a layer of fluorapatite is formed around the apatite crystal and this fluorapatite is assumed to be the thermodynamic governing phase during dissolution. The demineralixa...

The exchange of Ca2+ ions in hydroxyapatite (HAp) with Zn2+ into Zn-HAp is interest for applications ranging from bone tissue engineering to the use as a precursor subsequent ion-exchange reactions. Previous studies, using direct synthesis, showed that ~ 20 mol% can be incorporated HAp, before byproducts are observed. However, this realized at cost loss crystallinity and control over crystal si...

The magnetites and sulfides located in the rims of carbonate globules in the Martian meteorite ALH84001 have been claimed as evidence of past life on Mars. Here, we consider the possibility that the rims were formed by dissolution and reprecipitation of the primary carbonate by the action of water. To estimate the rate of these solution-precipitation reactions a kinetic model of magnesite-sider...

Abstract This work shows that the titanium dioxide coatings obtained by low-pressure cold gas spraying with use of sol–gel amorphous TiO 2 powder are characterized photocatalytic activity despite their partial content. Moreover, research outcome suggests decomposition rate organic pollutants is enhanced after long-term exposure to moisture. The condensation humidity test not detrimental continu...

Abstract Recent studies have identified gold nanoparticles in ores a range of deposit types, but little is known about their formation processes. In this contribution, gold-bearing magnetite from the well-documented, world-class Beiya Au deposit, China, was investigated terms microstructure and crystallography at nanoscale. We present first three-dimensional (3D) focused ion beam/scanning elect...

Abstract Pyrite geochemistry has proven useful for tracking changes in the composition and physico-chemical conditions of hydrothermal fluids ore-forming environments. Here, we investigated microtextural features chemical pyrite, a main Au-bearing phase Akeshi Kasuga deposits (Southern Kyushu, Japan), to better constrain processes these high-sulfidation epithermal Au deposits. Despite widesprea...