Unformatted text preview: of limestone caves 3‐Evaporites Evaporites are water‐soluble mineral sediments that result from the evaporation of water. Evaporites are considered sedimentary rocks. A‐Gypsum It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters, composed of calcium sulfate dehydrate, with the chemical formula CaSO4∙2H2O B‐Anhydrite From aqueous solution calcium sulfate is deposited as crystals of gypsum, but when the solution contains an excess of sodium or potassium chloride anhydrite is deposited if temperature is above 40°C Chemical formula: CaSO4 C‐Halite It is commonly known as rock salt. Halite forms isometric crystals. The mineral is typically colorless or white It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates. Chemical formula: NaCl D‐Potassium & Magnesium Salts 10 Geology & Geophysics in Oil Exploration Mahmoud Sroor Marl Travertine Coquina Gypsum Anhydrite Halite Geology & Geophysics in Oil Exploration 4‐Ironstones Ironstone is a fine‐grained, heavy and compact sedimentary rock. Its main components are the carbonate or oxide of iron, clay and/or sand. It can be thought of as a concretionary form of siderite. Ironstone also contains clay, and sometimes calcite and quartz. Freshly cleaved ironstone is usually grey. The brown appearance is due to oxidation of its surface. A‐Iron Oxides • Hematite: It is the mineral form of iron (III) oxide (Fe2O3), colored black to steel or silver‐gray, brown to reddish brown, or red • Magnetite: It is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides • Goethite: It is an iron oxyhydroxide (FeO (OH)), is an iron bearing oxide mineral found in soil and other low‐temperature environments, often forms through the weathering of other iron‐rich minerals Magnetite • Limonite: Limonite is an ore consisting in a mixture of hydrated iron (III) oxide‐hydroxide of varying composition...
View Full Document
- Spring '10
- Geology, Volcano, Tephra, Volcanic Ash, Geology & Geophysics, Mahmoud Ahmed Sroor