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Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks. Deposits are known to occur in strata from as far back as the Archaean eon. [16] Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins.
When the overall temperature of the cave started to drop below 56 °C (133 °F), the hydrothermal and sedimentary anhydrite crystals dissolved, and gypsum (CaSO 4 · 2 H 2 O) crystals formed. [7] The hydrated sulfate gypsum crystallized at an extremely slow rate over the course of at least 500,000 years, forming the enormous crystals found ...
The geology of East Sussex includes a number of natural resources, at Mountfield, Robertsbridge there is a gypsum mine which produces significant quantities of gypsum extracted from the Purbeck Beds. As previously mentioned the Wadhurst Clay holds ferrous ore which was extracted up to the 17th century.
Black alabaster is a rare anhydrite form of the gypsum-based mineral. The black form is found in only three veins in the world, one each in United States, Italy, and China. Alabaster Caverns State Park, near Freedom, Oklahoma, is home to a natural gypsum cave in which much of the gypsum is in the form of alabaster. There are several types of ...
The gypsum is mostly in the form of alabaster. There are several types of alabaster found at the site, including pink, white, and the rare black alabaster. This black alabaster can be found in only three veins in the world, one each in Oklahoma, Italy and China. Another form of gypsum can be found in the many selenite crystal formations. [4]
Location of the Swords and Crystal caves with the gypsum crystals within the conceptual block diagram of Naica mine. The Cave of the Crystals is a cave approximately 300 m (1,000 ft) below the surface in the limestone host rock of the mine, about 109-metre (358 ft) long, with a volume of 5,000 to 6,000 cubic metres (180,000 to 210,000 cu ft). [7]
Speleothems inside Optymistychna Cave. The entire cave lies under a 2 km square area in a layer of Neogene period gypsum that is less than 30 metres (98 ft) thick. [7] [9] The passages tend to be fairly small, no more than 3 metres (10 ft) wide and 1.5 metres (5 ft) tall for most, although at intersections they can be up to 10 metres (33 ft) tall. [7]
Gypcrust forms in a manner similar to that of caliche, which is composed of calcium carbonate.The development of gypcrust has three main stages. The first stage is primary crystallization of the surface brines or groundwater; the second stage is transportation and redeposition by wind or water; and the third stage is post-depositional alteration above or below the capillary fringe.