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Orange Flash of Opticon Filling in Emerald94 viewsFilling fractures with a resin of similar RI to the host emerald typically produces a color flash effect. In this case, an orange flash is seen. (Photo: R.W. Hughes)
Diamond86 views
Curved striae in synthetic ruby126 viewsCurved striae in synthetic ruby, seen under diffused lighting.
100 views
Lily-pad Inclusion in Peridot104 views
Sapphire, natural, Australia78 views
102 views
Knischka synthetic Ruby104 viewsDeveloped by Prof. P.O. Knischka, this synthetic ruby is recognizable in the rough crystal by its spindleshaped, multi-facetted shape. Facetted stones (these aren't yet widely distributed) may contain phantom-like clouds of dust particles (similar to those seen in Burma rubies).
Other more diagnostic internal features include swirls of colour; irregularly shaped, net-like liquid feathers; parallel negative crystals having- the same bipyramidal habit as the host crystal and appearing at the end of long crystal tubes; black, distorted hexagonal platelets of platinum and silver; and two-phase inclusions (with ill-defined void boundaries and conspicuous bubbles), this last feature being regarded as an identifying characteristic of Knischka rubies.
When visible on a spectroscope, an absorption band between 250 and 400 nm is a clear indication that the ruby is a synthetic (this band is more easily detectable on a spectrophotometer). The Knischka rubies that have been inspected so far show little iron content, and therefore have a high S.W. U-V transmission factor.
