39* Geological Society. 



3. Two tons of coals for the use of the Society : ens 

 from Wyken, near Coventry : the other from Petsall ii^ 

 Staffordshire, i'ropi William James, Esq. M. G.S. 



A communication from Arthur Aikin, Esq. Secretary, 

 entitled, «' Some observations on a bed of greenstone near 

 Walsall, Staffordshire," was read, and thanks were voted 

 for the same. 



The greenstone, which is the subject of this paper, is of ^ 

 (lark blackish-blue green colour ; has a gliirimerinor lustre, 

 and an uneven fracture, breaking info irreffulai iy 'vedge- 

 shaped blunt-edged fragments: it is tough, act|Uiiing a 

 kind of polish under the harnmer, is moderately hard, and 

 rather heavy. It strongly attracts the magnetic needle, and 

 effervesces on immersion in cold diluted muriatic acid. It 

 consists principally of felspar, mixed with calcareous spar. 

 With minute shining black grains of angite, and of horn- 

 blende. It is penetrated by nearlv vertical contemporaneous 

 slen !er veins of calcareous spar, and after a fevi' weeks 

 exposure to the air acquires a liver-brown colour, and falls 

 to pieces. 



It occurs in the Independent Coal Formation, but is 

 not CO extensive with that formation ; nor, indeed, in the 

 opinion «)f the author of the paper, is it to l)e con'iidered as 

 a ifuebed, but rather a lateral vein branching off from ^ 

 large dyke of greenstone that con es up to the surface, 

 dividing the colliery in which the greenstone bed is, from 

 another adjacent to it. 



On coHiparing the strata above and below the greenstone 

 with the very same strata that have been pierced througl} 

 in a part of the colliery where the greenstone does not 

 occur, it appears, That the bed of slaty clay, with balls of 

 ironstone lying upon the greenstone, does not materially 

 differ from the same bed where the greenstone is absent ; 

 but that the beds immediately /le/o'// the greenstone, present 

 very diflerent characters where they are covered by this 

 latter, from what they do where the contrary is the case^ 

 These beds are 1. Sandstone; 2. Bituminous shale with 

 slender seams of ccal ; and 3. A coal somewhat more than 

 a yard thick. Of thesje, the sandstone is considerably in- 

 durated : the bituminous shale is also indurated, entirely 

 deprived of bitumen, and is broken more or less into angu- 

 lar pieces, and mixed with ihe lower part of the sandstone 

 bed. The yard coal is also entirely deprived of bitumen, 

 is stained and iridescent on the surface of its natural joints, 

 and is more friable. These changes appear to accompany 

 the Buperposition of the greenstone bed through its whol« 



f ;«tent j 



