Photographic feature: Gypsum crystal mineralogy

Gypsum Crystal Mineralogy

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

General features

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

Research Paper: Gypsum crystals in Irish mudstone aggregate

George Matheson (Matrock Consulting) and Gareth Jones (Conodate Geology) have published a paper on the mineralogy of gypsum in aggregates that have undergone pyrite heave. The authors used advanced petrography to examine the form of gypsum and its relation to forceful or passive growth with regards to aggregate expansion.

The paper, titled “The habit and form of gypsum crystals in Irish mudstone aggregate affected by pyrite-induced swelling” follows previous presentations by Matheson, e.g., in December 2012:

Matheson, G. (2012). Pyrite-induced swelling. Annual Guest Lecture given to the Geotechnical Society of Ireland. 6.12.12, Engineers Ireland, Dublin. Click here to see original flyer.Read the rest

Sinkholes: Buried alive – Documentary featuring gypsum dissolution

Sinkholes documentary

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

BS 5930:2015: new guidance on sulfur-species

BS 5930:2015

On 31 July 2015, BS 5930:2015 “Code of practice for ground investigations” was published, replacing the former standard, BS 5930:1999+A2:2010 (Code of practice for site investigations). The BSI website states that:

“BS 5930:2015 deals with the investigation of sites in order to assess their suitability for construction and to identify the characteristics of a site that affect the design and construction of the project.  It also considers related issues including the environment and the security of adjacent land and property.”

“This is a full revision of the standard and introduces some principal changes…” [including] “…Compliance with BS EN 1997-1 and BS EN 1997-2 and related test standards…” [and] “…New information on geophysical surveying and ground testing and updated guidance on desk studies, field reconnaissance, ground investigations on contaminated ground and ground affected by voids.”

Guidance on sulfur-species

BS 5930:2015 provides considerable additional guidance on the presence and assessment of sulfur-species in geological materials compared to the 1999 version.… Read the rest

Geoscientist mag: Gypsum dissolution hazards

Gypsum Dissolution hazards

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:

“Caves in gypsum or halite are the exception.

Read the rest