Coscinodiscus asteromphalus, Watson and Sons

Coscinodiscus asteromphalus arrangement, Realgar
Coscinodiscus asteromphalus, Realgar

An arrangement of Coscinodiscus asteromphalus. Prepared by Watson and Sons Ltd. Mounted in Realgar. Some degradation to the mountant (as is often the case with Realgar slides), but still intact enough to image. The label on the slide says “In specially high refractive ……. of Realgar”. I’m not sure what the word after ‘refractive’ says, but it could be ‘preparation’ or ‘precipitation’. Olympus BHB microscope using white LED light. Arrangement imaged with a 4x Zeiss Planapo NA 0.16 objective using an Olympus Abbe condenser with the top lens removed. Single example imaged with a 20x Nikon Plan Apo NA 0.65 objective using an Olympus Aplanat Achromat condenser, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Canon EOS 5DSR camera with autowhitebalance. Single images (no stacking).

The other Realgar slides I have are strews, and I’ve never seen an arrangement in Realgar. In an article by Meakin in 1939 he mentioned that due to the way in which these slides were made “…only strews could be made due to the process of producing the realgar layer.”. If you have a Realgar slide with an arrangement, please contact me, I’d love to see another one.

Slide donated by Nigel & Lisa Ashby.