DIAMANTINE
Diamantine is the hardest polishing paste available. It is also generally used for the finest polishing. On steel parts these are called “black polish”. Diamantine is made from diamond powder.
In the history of watchmaking, diamantine has often been used for the finest polishing. At a time when cases were not as water-resistant as they are today, it was important to polish steel parts very finely, as this surface finish reduces the risk of oxidation.
Avantages: It is the hardest of the polishing pastes that gives the best results.
Disadvantages: Diamantine is relatively expensive.