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Derbyshire Blue John
Blue John (also known as Derbyshire Spar) is a semi-precious mineral, a rare form of fluorite with bands of a purple-blue or yellowish colour. In the UK it is found only at Blue John Cavern and Treak Cliff Cavern at Castleton in Derbyshire. During the 19th century, it was mined for its ornamental value, and mining continues on a small scale. Etymology The most common explanation for the name is that it derives from the French , meaning 'blue-yellow'. The story goes that Blue John was exported to France where it was used by ''ormolu'' workers during the reign of Louis XVI (1774–91). However, there is no archival record of any Blue John being exported to France, and the early ''ormolu'' ornaments which use Blue John were being manufactured by Matthew Boulton of Birmingham in the 1760s. An alternative origin of the name derives from an old miners' name for the zinc ore sphalerite, which they called "Black Jack". Thus, the unique blue stone mined in these caverns could easily ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cliff Blue Vein Bowl - Castleton Visitor Centre
In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs. An escarpment (or scarp) is a type of cliff formed by the movement of a geologic fault, a landslide, or sometimes by rock slides or falling rocks which change the differential erosion of the rock layers. Most cliffs have some form of scree slope at their base. In arid areas or under high cliffs, they are generally exposed jumbles of fallen rock. In areas of higher moisture, a soil slope may obscure the talus. Many cliffs also featur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
