404 A. Strahan — Explosive Slickensides. 



in others with a slight report ; and in some of the mines in th& 

 neighboarhood of Eyam, in Derbyshire, with loud reports, particu- 

 larly in Cracking-hole vein, in Haycliffe title .... where in the 

 centre of the vein, termed a shack vein, was a small white impalpable 

 (not effervescing) powder, called a mallion, a quarter of an inch thick, 

 which on being scratched, a loud explosion immediately ensued, 

 before which explosion a singing kind of noise was heard. By 

 setting a blast in the vein at a short distance from the mallion, after 

 the blast was fired, in a few minutes an explosion took place, when 

 a large quantity of the vein fell down. In the year 1790, a loud 

 explosion took place from a slide joint of Slickensides going across, 

 but not into the cheeks of the vein containing the mallion, which 

 caused on its being stirred the loudest explosion and the largest 



quantity of vein materials to come down The last great 



explosion was in the year 1805. It has sometimes happened that 

 persons have been maimed or even killed by this phenomenon ; 

 which, however, has not been noticed from Slickensides wher-e no 

 shale is incumbent.''^ ^ 



In writing of the mines on Hucklow Edge, William Wood refers 

 to the Hay Cliff, as " a mine distinguished for having contained in 

 great abundance, that extraordinary phenomenon in the mineral 

 world, provincially called Slickensides. . . . The effects of this 

 mineral are terrific : a blow with a hammer, a stroke or scratch with 

 a miner's pick is sufficient to blast asunder the massive rocks to 

 which it is found attached. ... A person named Higginbotham once 

 narrowly escaped with life, by incautiously striking this substance 

 in the above mine. Experienced miners can, however, work where 

 it greatly abounds without much danger. It is also known by the 

 name of Cracking- whole." ^ 



The phenomenon is referred to by W. Adam also, who supposes 

 that the slickenside has been produced by the rubbing of the rocks 

 against one another. " The intense heat generated by the motion of 

 such vast masses (expanding the air in its pores) may account for 

 its exploding when broken into, similar to lumps of glass when 

 suddenly cooled, which explode on being scratched or slightly 

 broken." ^ 



" To avoid the danger attendant on working in its immediate con- 

 tiguity, the miners use the precaution of merely making a small 

 incision or aperture, with the point of the pick, and then retire to 

 a place of safety, awaiting the result. In case of an explosion, it 

 generally takes place in ten or fifteen minutes, and by the force 

 attendant on which, considerable masses of ore, and even stuff, are 

 detached." * 



Sir Charles Lyell, referring to this subject in the 6th edition of 

 ^ An Account of the Explosion of Slickensides, by W. Watson, Edin. Journ. Sci. 

 new ser. vol. ii. p. 186, 1829. 



- The History and Antiquities of Eyam ; with a minute account of the Great 

 Plague, which desolated that village in the year 1666, by William "Wood, 8vo., 

 London and Derby, 2nd ed. 1852 ; 3rd ed. date not stated. 



3 The Gem of the Peak ; or, Matlock Bath and its Yicinity, etc., by "W. Adam^ 

 London, 1845, p. 419, footnote. 



* Mining Almanack for 1850, by W. English, London, p. 220. 



