Page:VCH Derbyshire 1.djvu/55

 GEOLOGY LEAD AND LEAD MINING The large number of old mines bears witness to the vast amount of mining which has been done in Derbyshire. The majority of mines have been worked out or abandoned through the difficulty of getting rid of water, the expense of obtaining the ore, and the great fall in the price of lead. The only mine at which any quantity of lead is being raised is the Mill Close near Darley Dale. It is in the upper beds of Mountain Limestone. The oldest mine in the county is probably the Odin near Castleton, which is reputed to have been worked by the Danes. The Romans raised and smelted ore in Derbyshire, and left traces of their work in pigs of lead with Latin inscriptions. The lead mining industry in Derbyshire is governed by curious customs and rights which have existed from time immemorial, and were confirmed by Acts of Parliament passed in 1851 and 1852. In certain parts of the county any one may search or dig for lead ore without asking for the owner's permission, and the owner or occupier of the land cannot claim compensation. This is subject to the condition that the miner finds ore and pays a dish to the barmaster. The miner is entitled to sufficient surface for his hillock, a way to the highway most convenient to the mine, and waterway to the nearest stream of running water. The only compensation the owner gets for the loss is the right to sell any other mineral except lead which the miner may bring to the surface. Galena is the ore of lead which has been mostly worked. It is found in rakes, pipes and flats. A rake vein is generally an almost vertical fissure in the limestone. The ore usually occurs in ribs with layers of calcite, barytes or fluor arranged more or less parallel to the walls of the rake. Sometimes it is found in isolated cubes in association with calcite or barytes. Pipes veins are irregularly shaped cavities or pockets in the lime- stone generally parallel to the bedding planes, and are often connected by a crack filled with clay or spar called a leader. They vary in size, and may be considered as the widening out of a rake or of a serin, which is a string of ore branching off from a rake and forming smaller veins. A flat is not so common as rake and pipe veins. It is generally found along the junction of two beds, and consists of a low flat chamber with the roof and floor separated by only a few feet. The lodes are richer and more numerous in the upper than in the lower beds of limestone, and most of the rich deposits of ore have been found in the beds of limestone immediately below the Yoredale Shales. In addition to galena the following ores of lead have been obtained in small quantities : mimetite, cerussite, pyromorphite and phosgenite. Small quantities of copper ore, black oxide ot manganese ('wad'), haematite, yellow and red ochre have been worked in the limestone. ii