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A pyrite cube (center) has dissolved away from a host rock, leaving behind trace gold Iron pyrite is unstable when exposed to the oxidizing conditions prevailing at the Earth's surface: iron pyrite in contact with atmospheric oxygen and water, or damp, ultimately decomposes into iron oxyhydroxides ( ferrihydrite , FeO(OH)) and sulfuric acid ( H
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
When atmospheric carbon dioxide (CO 2), or carbonate ions (HCO − 3, CO 2− 3 dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, Ca(OH) 2) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite).
A slab of pykrete Pykrete is made of 14% sawdust and 86% water by mass.. Pykrete (/ ˈ p aɪ k r iː t /, PIE-creet) [1] is a frozen ice composite, [2] originally made of approximately 14% sawdust or some other form of wood pulp (such as paper) and 86% ice by weight (6 to 1 by weight).
A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%). B Calculated values *Derived data by calculation.
Organisms release sulfide, which reacts with dissolved iron in the surrounding water, when they decay. This reaction between iron and sulfides forms pyrite (FeS 2). Carbonate shell material of the organism is then replaced with pyrite due to a higher concentration of pyrite and a lower concentration of carbonate in the surrounding water.
Water from the ground, lakes, or oceans seeps into the pores of organic tissue and forms a crystal cast with deposited minerals. Crystals begin to form in the porous cell walls. This process continues on the inner surface of the walls until the central cavity of the cell, the lumen , is completely filled.
In structural geology and diagenesis, pressure solution or pressure dissolution is a deformation mechanism that involves the dissolution of minerals at grain-to-grain contacts into an aqueous pore fluid in areas of relatively high stress and either deposition in regions of relatively low stress within the same rock or their complete removal from the rock within the fluid.