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Processing selenium in the laboratory

The following interesting statements are found at Wikipedia:

Several modifications exist
Selenium is considered a semi-metal
Above 60° C a glass like modification occurs
The forming above 80° C grey, semi-metal modification is the most stable form
Selenium occurs in nature as a native metal
Melting point 221° C
Mohs hardness 2

The Task

The provided sample was ultra-pure selenium. In order to comminute this sample, the Planetary Mono Mill PULVERISETTE 6 classic line was equipped with the 250 ml zirconium oxide grinding bowl and 15 x 20 mm grinding balls were chosen. Although we recommend in our technical documents a maximum feed size of 10 mm, the chunks shown in the photo are clearly larger though. For the pre-comminution no technology was available which excluded a contamination. Therefore the sample was added as shown.

Results after 5 minutes comminution

After a processing of 5 minutes at a maximum rotational speed (650 rpm), it was assessed and exactly as expected, a fine powder with several, few rough chunks was found. On the photo those are seen next to the coin (comparison of size) and on the lower rim of the photo. These chunks were sorted out and the remaining sample was ground further.