What does the technique of 'pulling' refer to in gem production?

The technique of 'pulling' refers specifically to the process where synthetic crystals grow from a seed crystal in a controlled environment. This method is pivotal in the creation of synthetic gemstones, particularly through processes such as the Czochralski process or the Verneuil process. In these methods, a small seed crystal is placed in a molten state of the desired material, and as the seed is slowly pulled upwards, crystals form around it, allowing for the growth of larger, high-quality synthetic gemstones.

This technique is significant because it enables the production of gems that have similar physical and chemical properties to their natural counterparts but are created in a laboratory setting. This contrasts with other methods listed in the choices, which focus on cutting, polishing, or drilling and do not involve the growth of crystals from seeds. Therefore, the choice accurately captures the essence of 'pulling' in the context of gem production.