First described in 1853 by August Breithaupt, Jarocite (also Jarosite) is a complex mineral with the chemical formula KFe3+3(OH)6(SO4)2.
Category Archives: Rock/fossil of the month
March 2010 – Redcar Submerged Forest
In January and February of 2010, beach deposits at Redcar – in an area roughly extending between the Information Center and Park Hotel – were stripped away by tidal scour revealing some infrequently exposed beds beneath the usual sand and pebbles.
At the base of the steps opposite the Information Center, and extending seaward for over [...]
on March 9, 2010 Leave a comment
February 2010 – Evaporites
Evaporites are non-clastic, or chemical sediments, created through the precipitation of dissolved salts from water. They most frequently occur at the site of a former large water body such as a lake or landlocked sea, on coastal plains (sabkha zones), or where rivers feed very arid desert areas. As the water involved slowly evaporates the [...]
on February 1, 2010 Leave a comment
January 2010 – Siderite
Iron carbonate (FeCO3), or siderite from the Greek sideros meaning iron, is a major source of ore for steel-making being usually low in sulphur and phosphorous, and high in manganese and/or magnesium.
This mineral is able to assume almost any colour but commonly brown, yellowish-brown, or grey specimens can be found. It occurs in Britain’s [...]
on January 6, 2010 Leave a comment
December – Galena
Galena, or lead sulphide (PbS), is a shiny grey mineral and the main ore of lead. Also known as Silver-Lead, it can be found in Carboniferous and Palaeozoic rocks around the world. In Britain it is found in Derbyshire, Wales, Upper Teesdale, Weardale, Cornwall, Cumbria, and the Yorkshire Pennines.
Use of this mineral can [...]
on December 1, 2009 Leave a comment
October – Mica
The name mica is thought to derive from the Latin word, micare – “to glitter”. This no doubt refers to the brilliant sparkle when light is reflected and refracted by this mineral.
More correctly, the Mica Group of minerals are sheet silicates. This means that instead of growing as a large crystal they form in [...]
on September 30, 2009 Leave a comment
September – Whinstone
Whinstone is a quarryman’s term for a variety of hard, dark-coloured, rocks including basalt and chert. Here, in the Tees Valley and Cleveland, the name refers to a hard rock that is very different from the soft sedimentary strata which make up the majority of the area’s underlying geology.
Around 58 million years ago, as [...]
on September 10, 2009 Leave a comment
August – Asbestos
During his now-infamous journey to the Orient Marco Polo is said to have been amazed when, following meals with wealthy Persians, the tablecloths were cleaned by exposing them to fire the cloths surviving the ordeal without a mark. The fibres from which the cloths were woven came to the Persians from the Hindu Kush, and [...]
on August 26, 2009 Leave a comment
June – Alum Shale
Alum Shale occurs within the upper 35 metres or so of the Whitby Mudstone Formation. A suite of rocks that originated as soft sediment accumulating on the floor of an ancient sea (the Tethys) which occupied this area between c.188 million and c.182 million years ago during the late Lower Jurassic phase of Earth’s geological [...]
on June 1, 2009 2 Comments
May – Sylvite
Sylvite, also called sylvinite when impure, is potassium chloride (KCl) in natural mineral form. It is colorless to white with shades of yellow and red due to inclusions, has a hardness of around 2.5 on Mohs’ Scale and has a distinctively bitter salty taste. Sylvite is a chemical sedimentary rock, laid down through the evaporation [...]
on May 10, 2009 Leave a comment