Microcrystalline gypsum

A rock of only micro chalk crystals

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This image shows extremely small gypsum crystals, visible only under the microscope: to the naked eye, this rock appears white and opaque.

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This particular sample was collected near the Dibona Hut and dates back to the upper Triassic  (approximately 230 million years ago).

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Gypsum is an unusual rock, and it is formed in very particular environments: it derives from the evaporation of sea water in an extremely hot and dry climate.

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This can only happen in tropical latitudes, in environments close to the sea similar to salinas, 

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and in extremely dry climates such as, for example, the shores of the Persian Gulf close to Abu Dhabi.

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Approximately 230 million years ago, the Dolomites would have been a coastal plain, at tropical latitudes and subject to an almost desert climate.

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If you want to get an idea of what that looked like, watch satellite images.In the sabkha of Abu Dhabi, gypsum is forming beneath a layer of dark mucilage that is clearly visible on satellite images.

References:https://www.environmentalatlas.ae/geographicInheritance/dunesAndSabkha

http://en.wikipedia.org/wiki/Sabkha

 

 

Name: Microcrystalline Gypsum
Classification: Chemical sedimentary rock, evaporite
Mineral composition: Gypsum
Fossils: None
Location: Dibona Refuse(46°32’5.09″N 12°4’21.20″E)
Formation: Travenanzes formation
Era: Upper Carnian (approximately 230 million years ago)
Depositional environment: Sabkha