Current Archaeology has a fascinating article about the "rediscovery of a series of rock samples collected during the Victorian period has allowed new analysis of some of the stones of Stonehenge. By Rob Ixer, Richard Bevins, Nick Pearce, and David Dawson".
One of the more interesting parts is the final putting to bed of the theory that the so-called Newall Boulder is a glacial erratic. A theory that was first raised in 1991 by G A Kellaway in "The older Plio-Pleistocene glaciations of the region around Bath." - Hot Springs of Bath, pp 243-41