It little matters for corona formation whether small particles are transparent or opaque. What does matter is their size and their shape.

Each year trees of the Northern forests release copious clouds of pollen. The pollen grains from a given tree variety usually have very similar sizes - ideal for corona formation.

Unlike water droplets, pollens are non spherical. Many have air sacs to assist wind dispersal and they are consequently become specially oriented as they drift in the air. The result is elongated coronae, sometimes with bright patches on their rings.

Pollens are comparatively large and so their coronae are small. Look close to a well shielded sun (take care of your eyes!) or, preferably, search for them in the reflection of the sky in a pool or dark glass.

Another pollen corona.