Fossils in amber (Part 2): Preparation and study

Dr David Penney and Dr David Green (UK) This is the second in a series of articles concerning fossils in amber. In the first, we focused on the biodiversity of organisms in the major deposits of the world, including the techniques available for distinguishing genuine fossils from fakes (see Fossils in amber (Part 1): Biodiversity). When the first fossil amber specimens were examined back in the 1600s, only very basic microscopy was available to examine the inclusions. In recent years, great progress has been made in amber preparation procedures, photomicroscopy and advanced imaging techniques, which can all now be employed in the study of fossils in amber. Optical properties of amber To understand the rationale for the preparation techniques described below, it is worth reviewing the way light passes through amber and the way that images are formed. Amber is usually transparent or translucent. The more transparent it is, the less the light is absorbed as it travels through the specimen. As opacity increases, more light is absorbed and inclusions become more difficult to see. Arthropod inclusions are visible because they have differing opacities and refractive indices to the enclosing amber. When light rays cross boundaries between media with different refractive indices (such as amber and air) they bend. If the surface is flat and polished, the light rays bend in a predictable manner and it is easy to see what lies within. If a surface is curved, irregular, undulating or scratched, the light rays bend in different directions, depending … Read More