Having worked as a forensic biologist in the past (my postgraduate specialization is in the microscopic identification of woods and other plant fragments) in relation to dozens of archeological projects, e.g. involving the Institute of Archeology, British Museum, Somerset Levels, National Maritime Museum, etc., I have to support Fibula Mattock observations here.

Careless excavation can totally destroy the integrity and mapping of a site. Besides metals, there may be bones, pottery and implements not to mention scraps and pieces of organic material such as leather, fibres, woods (especially difficult to work with if waterlogged and compacted) and this is why trained and scrupulous archeologists take such care on a site and carefully monitor and look after volunteers and helpers. It only takes a second to put beyond scientific analysis potentially important and seemingly mundane artefacts that can provide vital clues or evidence regarding a site. Just to give a small example: on a maritime excavation of a wrecked ship, the identification of woods, plants remains, fibres, etc. can give important information on trading routes, ports of call, etc.

Best regards,

mooman