Padparadscha
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Padparadscha is a pinkish-orange to orangy-pink coloured sapphire, with a low to medium saturation and light tone, originally being mined in Sri Lanka, but also found in deposits in Vietnam and Africa. Padparadscha sapphires are very rare, and highly valued for their subtle blend of soft pink and orange hues. The name derives from the Sinhalese word for lotus blossom. Along with Rubies they are the only corundums to be given their own name instead of being called a particular coloured sapphire.
Fabrication
Because of its rarity, it is frequently fabricated via synthetics in laboratory settings, or on regular pink or orange sapphires by a process of berylium surface diffusion. This diffusion process involves heating the stone along with crushed chrysoberyl, the source of the beryllium in the treatment.
The vast majority of padparadscha sapphires (and most other colors of sapphire) are heated in varying temperatures to enrich color and improve clarity. While this may have a negative effect on the price of the stone, it is an accepted practice so long as it is disclosed to the buyer in the process of the sale.
Treating stones with surface diffusion, however, is generally frowned upon; as stones chip or are repolished/refaceted the 'padparadscha' coloured layer can be removed. (There are some diffusion treated stones in which the color goes much deeper than the surface, however.) The problem lies in the fact that treated padparadschas are at times very difficult to detect, and they are the reason that getting a certificate from a reputable gemological lab (e.g. Gubelin, SSEF, AGTA, etc.) is recommended before investing in a padparadscha.
The rarest of all padparadschas is the totally natural variety. No beryllium, or other treatment, and no heating. To find a stone that is certified by a reputable lab as being completely natural is extremely rare and will be very expensive. High quality, notheated and nottreated natural padparadscha sapphires will start off in the range of $5,000 per carat and rise by size, color, tone, cut, and clarity, to $20,000–30,000 per carat.
Properties
- Composition: Al2O3
- Mohs hardness: 9
- Specific gravity: 4.00.
- Refractive index: 1.7862–1.770.
- Crystal system: Hexagonal (trigonal)
- Colors: Mixture of pink and orange
- Pleochroism: Weakly dichroic: two shades of the body color
- Phenomena: None
- Treatments: Often heated; surface diffusion
References
Hall, Cally (1994). Gem Stones. DK Publishing. ISBN 1-56458-498-4