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geological walk, Blease Fell, Threlkeld, Cumbria, NY2927 -- Rock, hand specimen of Skiddaw mudstone, moderately metamorphosed to slate with crystals of chiastolite, from Roughten Gill, Blease Fell, Threlkeld, Cumberland, NY29832730, 12 October 2012.
Skiddaw group, mudstone; Ordovician, Llanvirn/Arenig.
Chiastolite is a variety of andalusite, aluminium silicate, Al2SiO5.
(photo 12.10.2012)