On the occurrence of a Boulder of Granitoid Gneiss, or Gneissoid Granite, in the Halifax Hard Bed Coal

Abstract

From time to time during the last thirty years, boulders of quartzite and other hard rocks, having quite a distinct structure from that of any native rock of the district in which they occur, have been found in the coal beds. Many years ago, before the great importance of these boulders from coal beds was recognized, a fine specimen was found in the Hard Bed Coal at Dam Head Pit, in Shibden-dale, near Halifax. At that time having no means of submitting it to microscopic analysis, the most notable feature about it was its spherical and highly polished form. It was a hard white rock streaked with patches of darker hue, and of about the size of an orange; it had evidently been subjected to a great deal of attrition. About the same time, my friend, Mr. George Lister, had a fine quartzite boulder brought to him which was found in the Low Moor (near Bradford) Better Bed Coal. It was about the size of an ordinary football, and he informs me that the boulders in this locality were not very rare. Since that time boulders of quartzite and other rocks have been found in coal beds in various places in the Midland Coal-fields, and also in Lancashire and Derbyshire, some of which were described by Professor Bonney in his presidential address to the Geological Section of the British Association at Birmingham in 1886. In the spring of last year two or three quartzite boulders were recorded by Mr. C. ...