Diatoms (fossil, Renkum) in darkfield.

Diatoms can be found in water…but also in the soil. With a lot of help I succeeded making a permanent mount of such a (cleaned) sample in Pleurax. Pleurax is a mounting medium with a very high refractive index-1.73-, similar like Zrax and Naphrax.
In Holland, diatomaceous earth has virtually disappeared, through the years it has been used for production of e.g. dynamite, toothpaste and for filtration. Therefore very nice to look at this Renkum sample. Because Renkum is kind of famous, the diatoms are quite easy to identify, I found:

1. Epithemia turgida
2. Pinnularia nobilis
3. Pinnularia nobilis
4. Gomphonema acuminatum
5. Stauroneis phoenicenteron
6. Cymbella cuspidata

All were taken with darkfield and a 100x iris objective. I wanted to use a 1,3 Na darkfield condenser but somehow this did not work. The 0.8 Na condensor was okay, of course the diaphragm in the objective had to be partially closed. You might have noticed picture 6 is inverted darkfield.