308 LIAS Or ENGLAND AND WALES 
Iron Pyrites andMarcasite (Rhombic Iron Pyrites) are found more especially 
in the Lias shales. They are most abundant in the shales of the Lower Lias. 
At Black Ven, near Lyme Regis, there .is a " Metal Bed," and material derived 
from this and other layers, was formerly collected during the winter months, for 
the preparation of copperas (sulphate of iron), sulphuric acid, and sulphur. 
Examples of Marcasite from Lyme Regis are sold to visitors as " Angel's 
Wings." 
In the year 1755, spontaneous combustion occurred in the bituminous shales 
of the Lower Lias at Charmouth.* This took place among fallen masses of 
the strata, owing to the decomposition of pyrites. In 1890, similar combus- 
tion took place further east, and in the "Daily Graphic " of Feb. 19th, there 
appeared a picture of the " eruption " of Golden Cap. 
Selenite occurs in the Lias clays, but most abundantly in the Upper Lias 
in Northamptonshire and Leicestershire. 
Calcite is found plentifully on the joint-faces of the limestones, in crevices 
of the rocks, and lining the interiors of Mollusca aud other fossils. Nail-head 
ppar, a peculiar form of crystalline carbonate of lime, is met with in the 
Upper Lias of Northamptonshire. This form presents the " cone-in-cone " 
structure ; the surfaces of the cones being fretted with irregular crystalline 
coats, due perhaps to a kind of "concretionary crystallization."f Seams of 
fibrous carbonate of lime, known as " Beef," also occur in the Lias clays. 
(See p. 277.) Small concretions of the same substance, are known as " Race " ; 
and this often has a septarian structure. 
Barytes (Heavy Spar) occurs in the Cherty Lias of Harptree ; and it has 
been recorded from the Lower Lias near Gloucester.^ (See p. 98.) 
Quartz crystals and Chalcedony occur in the Lower Lias of Glamorgan- 
shire, and in the Cherty Lias of Harptree. 
* Buckland and De la Beche, Trans. Geol. Soc., ser. 2, vol. iv. p. 23. 
f See also G. A. J. Cole, Mineralogical Mag., vol. x. p. 136. 
I Conybeare and Phillips, Geol. England and Wale?, p. 265. 
