Czochralski Process (Crystal Pulling Technique)

Also known as the crystal pulling technique has a number of technical applications, since large crystals of good purity and optical homogeneity are obtained.

How gemstones are synthesized by czochralski process?

  • The source material is melted in a container (usually made of iridium) in an inert-gas atmosphere.
  • A rotating rod with a seed crystal is lowered until it touches the melt.
  • It is then slowly raised, allowing the molten source material, to solidify as the seed is slowly pulled from the melt.
  • The product obtained is a tabular boule which is virtually flawless.
  • Crystals which have lower melting points can be synthesized in the open, while high melting materials require a shield to control heat loss.

Gemstones synthesized by this method are:

  1. Synthetic Corundum (Synthetic Ruby and Synthetic Sapphire)
  2. Synthetic Alexandrite
  3. Yttrium Aluminium Garnet (various colours)
  4. Gadolinium Gallium Garnet (various colours)

Identification:
When present characteristic inclusions include gas bubbles, curved lines and curved colour banding. Y.A.G. and G.G.G. have characteristic properties.