On this how to I will try to explain how to polish a watch crystal using diamond lapping paste . The tubes were bought off ebay in case you were wondering... They are suppose to remove scratches from sapphire crystals. For my test I used a Swatch with a mineral crystal , because my sapphires are scratches free :)  The rule of thumb is , the deeper the scratch the higher micron paste you need.  For this test we used micron 3 ,5 and 2.

Start with micron 3 first , apply it and rub your crystal for 10 minutes. Then  , go to a higher grade micron if needed and last polish it with micron 2 . Some light scratches from the mineral crystal are gone , where some others are still there. Reason for that I believe is because this stuff is not suppose to work on mineral crystals.