> And if I could put my hand on my copy of 'British Regional Geology: > Orkney and Shetland' then I'd mention a volcanic vent or two...but I > can't so I won't. I now have, so I will! In case anyone is interested, it's ISBN 0118801619 and the British Regional Geology books seem to turn up often and very cheaply in second hand bookshops. The series is recommended if you have an interest in British geology - they go into quite a bit of detail (150 pages for Shetland and Orkney) with clear fold-out geological maps, etc. "Several small volcanic vents have been mapped in the area which extends from south-eastern Hoy and South Ronaldsay north-eastward to Deerness in south-east Mainland. There is also a cluster of vents and volcanic plugs in northern Hoy. In addition, a number of small crypto-vents have recently been recorded at Harra Ebb on the west coast of Mainland." Apologies for any typos. There are also some small areas with siltstones and shales, such as at Quoyloo. I don't think there would be any slate in Orkney, though. Martin -- Martin McCarthy /</ http://www.non-prophet.org marty@ancient-scotland.co.uk \>\ http://www.ancient-scotland.co.uk /</ http://www.ehabitat.demon.co.uk