The appearance of asterism can be produced on almost any transparent cabochon by cutting hundreds of fine grooves into its base. The grooves are usually cut in three directions with a diamond tool, and a mirror or a mirror-like coating is attached to the back. This creates a 6-rayed star of reasonable intensity. The mirror on the back of the stone and the appearance of the star is quite easy to identify. Usually synthetic gemstones are used in this imitation.
The most effective imitation star stone is made by placing a hollow cabochon of synthetic corundum over a piece of asteriated natural corundum, and then closing the back with a third piece. Once assembled and set in a piece of jewelry the girdle plane can be hidden by the setting. Sometimes a slice of black star corundum is glued to the back of the cabochon of synthetic corundum. The assembled stones can easily identified by their separation planes.
Another good imitation star stone is made up of a white opaque glass which is pressed into a mold to form cabochon with six raised ridges on the crown. The ridged cabochon is then coated with a thin layer of deep blue glaze which barely covers the ridges. The finished stone has a very similar appearance to a natural star sapphire with the star on or just below the surface. The stones are easy to identify because the stars does not move or roll across the surface when the stone is turned. Physical constants are typical of glass, not corundum.
Star diopside and star enstatite are two less-known inexpensive stones, which are often confused with one another. Both may display four rayed stars which meet at almost 90º. The reason for confusion is that they are frequently mixed into the same lots and sold as black stars. Star diopside usually display very sharp star, while enstatite may show weaker more diffused star and a unique bronzy sheen. Enstatite may also display eight rayed star.
No comments:
Post a Comment