To a large extent luck is a variable...nature will produce what it will. However, modern periculture farms can control certain variables to enhance the outcome: 

• Selection of the optimal mollusk species for the environment.
• Determining the duration of the pearl development cycle and thus the thickness of the nacre coating.
• Selection of the optimal site for the pearl farm.
• The skill of the technician who implants the nucleus.
• Maintaining and caring for the health of the oysters.
• Altering environmental conditions such as water depth and temperature to enhance the quality of the nacre.
• Final cleaning and polishing, bleaching and other processes that some pearls undergo.