Aydin and David, The orange color is probably not original. Organic pigments don't usually last for thousands of years. It may be iron oxide (rust) instead. We had a Conch-L discussion on "Red shells, blue shells" a year or two ago. When referring to the age of beach shells, I meant ordinary beach shells. The Pliocene Epoch ended about 2.0 million years ago; the Miocene Epoch about 5.1 million years ago, according to Harland et al. (1982). So any Chesapecten shells you see are more than two million years old. If you are interested in Michal Kowalewski's work and in what you can do with long-dead shells, consult the website of the CEAM taphonomy group at the University of Arizona, where he researched before finding a job at Virginia Tech. He did a lot of work in the Gulf of California (Mexico), and also in Brazil. Michal says that growth bands of shells can be used like tree rings, in this case as a record of past temperature and salinity. Since one shell bank can contain abundant shells ranging in age from the present back to several thousand years ago, we can in principle decipher the climatic history of a location over a period of thousands of years. This could be very useful in determining the natural state of areas for which we have no data before they were changed by nearby agriculture, industry, housing developments, etc. But this research is very new -- and you read it first on Conch-L! Andrew K. Rindsberg Geological Survey of Alabama Reference Harland, W. B., Cox, A. V., Llewellyn, P. G., Pickton, C. A. G., Smith, A. G., & Walters, R., 1982, A geologic time scale: London, Cambridge University Press, xi + 131 pp.