Flux Fusion Process

This method was developed only in the late 1930's and has since been perfected to a great extent.

  • A flux is a material that lowers the melting point of a substance with which it is mixed.
  • Some materials are quite insoluble in high temperature water, but are soluble in a flux.
  • The common fluxes used are lead fluoride, lithium molybdate and boron oxide.
  • Flux materials have fairly toxic fumes and are also very reactive materials.

How gemstones are synthesized by flux fusion process?

  • In most cases the crucibles are made of platinum, but iridium and graphite are also used.
  • Powdered ingredients are mixed with the flux in a platinum crucible.
  • On heating, the flux melts and becomes a powerful solvent for the other ingredients which also melts.
  • Cooling and evaporation causes crystallization of the molten material with or without the use of seed crystals.
  • As the growth is slow and equipment costs are high, these synthetics are expensive when compared with those by the methods discussed earlier.

Gemstones synthesized by flux fusion with its identification.

  • Synthetic Emerald:
    • The characteristic inclusions seen are flux fingerprints in the form veils and droplets or globules, hexagonal and / or triangular platelets, parallel growth structures or venetian blind effect, seed plate, spicules and included crystals.
    • Earlier flux emeralds have a lower R.I. = 1.56 - 1.565, D.R. 0.005. Recently available flux emeralds tend to have similar R.I.'s as the natural counterparts.
    • Earlier flux emeralds have a lower S.G. = 2.66. Recently available flux emeralds tend to have similar S.G.'s as the natural counterparts.
    • Flux emerald with high chromium content exhibit a strong red transmission to light, appear strong red through the Chelsea filter, and appear strong red under ultra violet light.
    • A few of the well known producers of these emerald are P. Gilson (France), G.F. Chatham (U.S.A), Zerfass, Lennix, Seiko and Russia.
  • Synthetic Corundum (Synthetic Ruby / Synthetic Sapphire):
    • Synthetic corundum has similar physical and optical properties as the natural counterparts.
    • Under magnification - flux fingerprints in the form veils and droplets or globules, flux droplets maybe whitish or orange (Ramaura) in colour, hexagonal and / or triangular platelets, parallel growth structures, zoning characterised by process, seed plate, spicules and included crystals.
    • A few of the well known producers of these rubies are Kashan (U.S.A), Chatham, \/ocera (Japan), Lechleitner (Austria), Ramaura, Knischka, Duoros (Greece), Tairus, Russia etc.
  • Synthetic Spinel:
    • Synthetic spinel has similar physical and optical properties as the natural counterparts.
    • Synthesized in red and recently blue varieties.
    • Under magnification flux droplets and veil like flux fingerprints are seen.
  • Y.A.G.:
    • Colourless when pure (without any dopants) - diamond simulant.
    • Isotropic character.
    • The S.G. is 4.55 - 4.60
    • Dispersion - 0.028
    • Flux veils under magnification.
  • Synthetic Chrysoberyl:
    • Synthetic chrysoberyl has similar physical and optical properties as the natural counterparts.
    • Synthetic alexandrite and synthetic chrysoberyl cat's eye have been synthesized.
    • Flux fingerprints, fine dust like pinpoint inclusions and droplets are seen under magnification.
    • Synthesized by Creative Crystals, Ramaura, Seiko, Kyocera (Inamori), Russia.