Tanzanite Properties
Specific gravity: 3.35
Hardness: 6-7
Refractive Index: .690 - 1.700
Optical: Strongly trichroic, showing strong blue, purplish red and greenish yellow with a dichroscope.


SYNTHETIC SAPPHIRE
(often referred to as Chortanite)

This lab-grown corundum is fine-tuned to look like bluer tanzanite. It's far harder than tanzanite, registering 9 on the Mohs hardness scale. But it lacks tanzanite's and synthetic forsterite's strong pleochroic showing of blue and purple.

Padparadscha is a special variety of gem corundum, featuring a delicate color that is a mixture of pink and orange - a marriage between ruby and yellow sapphire. The question of just what qualifies for the princely kiss of "padparadscha" is a matter of hot debate, even among experts.

Today, padparadscha is narrowly defined by Western gemologists as a Sri Lankan sapphire of delicate pinkish orange color. But the original use of the term was somewhat different.

Padparadscha is derived from the Sanskrit/Singhalese padmaraga, a color akin to the lotus flower (Nelumbo Nucifera 'Speciosa'). Most lotus blossoms are far more pink than orange, and in ancient times, padmaraga was described as a subvariety of ruby ( cf. the Hindu Garuda Purana ). Today, some define the gem's color as a blend of lotus and sunset.

A further complication is with orange sapphires from Tanzania's Umba Valley. While they are orange, their color tends to be much darker than the ideal, with brownish overtones. Thus most traders do not feel they qualify as true padparadschas.

Color. Unlike other rubies and sapphires, the finest color of padparadscha is not directly a function of color intensity (saturation). The most valuable padparadschas display a delicate mixture of pink and orange.

Lighting. Sapphires generally look best viewed with fluorescent light or daylight (particularly around just after sunrise and before sunset). Incandescent lights, whose output is tilted towards the red end of the spectrum, do not do most blue sapphires justice.

Clarity. In terms of clarity, padparadscha sapphires tend to be cleaner than ruby. Look for stones which are eye-clean, i.e., with no inclusions visible to the unaided eye.

Because of the pastel shades of most padparadschas, any inclusions will be quite visible. Thus again, the emphasis is on eye-clean stones.

Cut. In the market, padparadschas are found in a variety of shapes and cutting styles. Due to the shape of the rough, stones are often cut with overly deep pavilions. Ovals and cushions are the most common, but rounds are also seen, as are other shapes, such as the emerald cut. Slight premiums are paid for round stones.

Cabochon-cut padparadschas are not often seen (this cut is used for star stones, or those not clean enough to facet). The best cabochons are reasonably transparent, with nice smooth domes of good symmetry.

Prices. Padparadscha is one of the world's most expensive gems, with prices similar to those fetched by fine ruby or emerald. But like all gem materials, low-quality (i.e., non-gem quality) pieces may be available for a few dollars per carat. Such stones are generally not clean enough to facet. Prices for padparadschas vary greatly according to size and quality. At the top end, they may reach as much as US$30,000 per carat.

Stone Sizes. Padparadscha sizes tend to be similar to ruby. Probably the largest fine stone known is the 100.18-ct. oval in New York's American Museum of Natural History. But any fine untreated padparadscha of quality above two carats is a rare stone. Fine untreated padparadschas above five carats can be considered world-class pieces.

Phenomena. While star sapphires in other colors are common, star padparadschas are practically unknown. This is because yellow and orange sapphires from Sri Lanka generally lack the concentrations of well-defined silk necessary to produce distinct asterism.

Sources. The original locality for padparadscha is Sri Lanka (Ceylon) and many purists today believe the term should be restricted only to stones from Ceylon. However, fine stones have also been found in Vietnam's Quy Chau district, Tanzania's Tunduru district, and Madagascar. Stones from these latter three areas are often heat-treated and may reach rich "orange-juice" or "papaya" oranges that are quite beautiful.

Tanzania's Umba Valley also produces orange sapphires and some dealers argue that these qualify as padparadschas. However, their color tends to be much darker than the ideal, with brownish overtones. Thus most traders do not feel they qualify as true padparadschas.

Enhancements. Today, many padparadscha sapphires are heat-treated to improve their appearance. The resulting stones are completely stable in color. In lower qualities, heat treated stones sell for roughly the same as untreated stones of the same quality. However, for finer qualities, untreated stones fetch a premium that is sometimes 50% or more when compared with treated stones of similar quality.

A fraudulent treatment sometimes seen is where a pink stone is irradiated to give it a padparadscha color. The resulting color is unstable and will fade with prolonged exposure to sunlight. Other treatments, such as oiling, dying and surface diffusion are seen on occasion.

Beginning in late 2001, sapphires of padparadscha colors began appearing from the ovens of Thai burners. It was later found that these gems owe their color to a form of outside-in bulk ('surface') diffusion.

As with all precious stones, it is a good practice to have any major purchases tested by a reputable gem lab, such as the GIA or AGTA , to determine if a gem is enhanced.

Imitations. Synthetic padparadscha sapphires have been produced by the Verneuil process since about 1908 and cost just pennies per carat. They have also been produced by the flux, hydrothermal, floating zone and Czochralski processes, but such stones are rarely encountered. Doublets consisting of natural sapphire crowns and synthetic sapphire pavilions are sometimes seen, particularly in mining areas. Synthetics are also common at the mines, in both rough and cut forms.

PROPERTIES:
Composition: Al2O3
Hardness (Mohs): 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

Handling:
Generally no special care needed; all ruby and sapphire jewelry can be cleaned using soapy water, or detergent. Make sure to rinse thoroughly afterwards as detergents can cause dermatitis and allergic reactions. Enzyme cleaners should be avoided for the same reasons. Brushing with an old tooth brush to remove dirt and grease will also help. Cleaning agents containing chlorine may have a detrimental effect on low-carat gold alloys, so are best avoided.

Enhancement:
Frequently heated; occasionally irradiation, oiling, dying, surface diffusion.