In the Indian Ocean, off the coast of southeastern Africa, across from Mozambique and northeast of the Republic of South Africa lies Madagascar, the fourth-largest island in the world. (Only Greenland, New Guinea, and Borneo are bigger.) Inhabited by 16 million people spread out over roughly 225,000 square miles, it's known mostly for vanilla and coffee, but its wealth of gem deposits may change that.
History. Two hundred million years ago, at the beginning of the Mesozoic period, Madagascar was bordered not by the Indian Ocean and the Mozambique Channel but by eastern Tanzania, southwestern India, and Sri Lanka. But continental drift pushed Madagascar away from the African continent and sent India crashing into the Asian continent (creating the Himalayas). This may explain why the gemstones found in all three regions are so similar.
The British controlled the island during World War II, but the French—who had made the island a protectorate in 1885—moved back into power after the war. Madagascar gained independence in 1960, but its leaders since then have been known primarily for their corruption. After Madagascar's 2002 elections, both candidates declared victory and riots ensued. It took nearly six months to restore order, and the country's infrastructure had been ripped apart. It will take years to undo the damage, making it difficult to acquire the island's vast quantities of fine gem material.
Alluvial gem deposits have been noted on the island since the early 1900s. It is said that most of the sapphire obtained there today comes from deposits listed in publications of the 1920s. Many of these deposits are located in the Ilakaka region in the central southwest section of the island. There also are world-famous pegmatites found in the central highlands, just south of the capital city—a longtime source for beryls and tourmalines, etc. Consistent production is difficult to establish, because whenever a more profitable gem deposit is found—which happens every few months—miners pack up and leave, stranding thousands of carats of less economical gems in the rivers they just left.
Color variations. When one hears "sapphire," one naturally assumes that you're talking about blue stones. But in Madagascar, every color of the rainbow is available, from the more traditional blue, pink, green, yellow, and orange to the pastel violets, peaches, and mahoganies.
Qualities. Color is sapphire's most important quality; the more saturated and pure the hue, the more it's appreciated. Top-color Madagascar blues, greens, yellows, and pinks typically are strong in saturation, medium dark in tone, and similar to top-quality Sri Lankan material. The pastels are quite nice and very popular, but they don't get top-quality marks.
Values. Sapphire's value depends mainly on color, but country of origin also affects value. Madagascar can't compete with the mystique of Kashmir, Burma, or even Montana and Sri Lanka, but it can compete on color and quality.
Pricing. The vast quantities of Madagascar sapphire keep good-quality sapphire prices very affordable, especially in the pinks. According to The Guide, 1-ct. to 2-ct. blues of fine quality range in price from $1,300/ct. to $2,000/ct. Pinks range from $175/ct. to $450/ct.
Enhancement disclosure. One of the most important disclosure issues of the past year concerns the new bulk diffusion treatment coming out of Chanthaburi, Thailand. The enhancement itself originated with Madagascar material. When Madagascar yellow sapphire rough was heat-treated with yellow chrysoberyl rough (which had been mistaken for sapphire), beryllium from the chrysoberyl migrated into the sapphire, creating a more intense yellow. After the discovery, various colors of sapphire were heat-treated along with chrysoberyl rough to produce better, more saturated colors—anything that would benefit from the addition of a yellow enhancement. Of most importance was the heat-treating of pink Madagascar sapphire with chrysoberyl to create a pinkish orange padparadscha color, the most sought-after of all the sapphire colors. However, once it was determined to be a diffusion treatment, demand (and therefore prices) for the material dropped dramatically.
Heat-treatment of sapphires to improve color as well as clarity, is generally accepted, but diffusing elements into the gem is not. Gems enhanced through diffusion of foreign elements—a process now called "bulk diffusion"—are subject to mandatory disclosure in the United States, and they are less valuable. Unheated sapphires—as dealers will quickly tell you—are the most valuable.
Determining whether a sapphire has been heat-treated or not can be difficult—and bulk diffusion treatment is even more difficult to identify. Traditional heat treatment of the pink sapphire from Madagascar requires less than "normal" heat to improve its color. The typical telltale signs of heat treatment, such as exploded crystals with accompanying stress fractures ("halos"), are not seen in the "lightly" heated Madagascar pinks.
Because there is a dramatic price difference between treated and untreated sapphire, it is recommended that all enhancements be disclosed to your clients.
Care and cleaning. Sapphires are difficult to scratch—they have a hardness rating of 9 on the Mohs scale. Only diamond, synthetic moissanite (9.25), or another sapphire can harm a sapphire's finish. Ultrasonic and steam cleaning are recommended for cleaning sapphire, but value dictates caution when caring for sapphires set in jewelry.
Bench settings and precautions. Bench jewelers should always be aware of the unusual, but transparent sapphires in general can withstand most repair and cleaning methods. Appearances, however, can sometimes be deceiving. Because the bulk diffusion treatment discussed above can concentrate color in the surface layer of the gem, the color can be lost if the gem has to be repolished. Examination of all colored sapphire is an appropriate precaution prior to working on what could be a treated stone.
Recommended reading. For more information, see Ruby & Sapphire by Richard Hughes, 1997, RWH Publishing, Fallbrook, Calif.; and "Storm over Sapphire," JCK, July 2002, p. 90.