On Rutile in the Dogger

Abstract

In several papers by the present author alone or in collaboration with Dr. J. E. Hemingway, mention has been made of the abundance of the titanium minerals, rutile, anatase, and brookite, in the Middle Jurassic sediments of Yorkshire. One of these papers dealt with brookite crystals from the Dogger, and the present one will describe briefly the types of rutile crystals from the same formation; partly because these show interesting peculiarities, and partly, as a subsidiary object, because it has appeared during this investigation that the descriptions given in most of the books of reference of sedimentary rutiles are somewhat inadequate, several striking features found to be widely prevalent not being mentioned in any of them, while other points are dealt with very briefly by most authors. A beginner in sedimentary petrography, confronted with a heavy mineral concentrate of this kind, might find considerable difficulty in identifying the crystals of rutile.