stones

The start size with a length of 8 mm is suitable for a direct grinding. If bigger stones should be fed ( > 1,5 cm length), possibly a pre grinding with Jaw Crusher PULVERISETTE 1 might be required.

As desired, the sample got ground with a grinding set made of hardmetal tungsten carbide. If a further analysis will not be disturbed by abrasion of steel, a grinding set made of hardened steel will only need a short time longer to achieve an equal fineness.

After only 1 minute of dry grinding, the sample starts sticking lightly to the ring and the core of the grinding set.

This uses to happen after the majority of particles reached a fineness of < 30 µm. Interacting forces between fine ground particles will become bigger as their own g-force. Therefore, particles will stick to each other and become compressed by the used grinding set. These clusters of particles also contain bigger particles which will not be ground any further.

For this, much finer grinding results can only be achieved by grinding in suspension.