This photographic article considers the habit and mineralogy of gypsum crystals from a glacial till deposit and Jurassic rock strata in Northamptonshire (UK). The crystals display excellent examples of fish-tail and swallow-tail twinning as well as unusual features such as deformed twin planes, clay inclusions and ripple-like textures.
Gypsum in the Oadby Member Glacial Till
Coarse selenite (prismatic/well-formed gypsum) crystals, up to 100mm in length, are present within the Oadby Member glacial till exposed within a quarry local to the Weldon area of Northamptonshire, UK. Gypsum crystals from this area range in size from 5mm to 150mm (typically 30-50mm) and are generally colourless to light grey.… Read the rest
Tonight, at 20:00 GMT on Channel 5 (UK), the documentary “Sinkholes: Buried Alive” will feature the hazards associated with the dissolution of ground materials, including gypsum. The documentary summary is below:
“Sinkholes can occur gradually when the surface subsides into bowl shaped depressions or suddenly when the ground gives way. These geological hazards have swallowed highways, apartment buildings, horses, camels, even golfers, with monster-size holes cracking the earth from Siberia to Louisiana. Filled with compelling eyewitness video of dramatic collapses, and following scientists as they explore the underlying forces behind these natural disasters, this documentary travels the globe to investigate what it’s like to have your world vanish beneath your feet.”
The documentary will focus mainly on limestone sinkholes in Florida and a major salt-mining induced sinkhole at Bayou Corne, Louisiana.… Read the rest
This month’s issue of Geoscientist, the magazine of the Geological Society of London features another potential problem resulting from sulfur-species in geological materials – gypsum dissolution.
In the article, titled “A hole lot of trouble” Andy Farrant and Tony Cooper discuss the problems of rock dissolution and the formation of subsidence features such as sinkholes. One of these soluble minerals is gypsum, of which there are significant Triassic and Permian deposits in the UK. The authors provide an excellent national-scale map of soluble rocks in England, Wales and Scotland. A quote from the article: