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Phenomena in Songea Sapphires

Updated: Jul 7, 2020

By Alissa Young, GG

On behalf of Milstead Gems LLC

Songea sapphire, color change sapphire
Songea sapphires cut by Tia Ong (IG: @pebblesprout)

Deep in the heart of East Africa just south of the equator lies a country of astonishing riches. Both ancient in history and young in name, Tanzania hosts a treasure trove of precious gemstones, from the violet blue tanzanite that shares its name to the coveted Malaia garnets first discovered in the Umba Valley. However, along the southwestern region of the country near the border to Mozambique hides a stunning gem that has only recently gained the attention it deserves. It is here that we find the Songea sapphire.

Map of Songea

Tanzania has seen its fair share of turmoil since it was first founded as a sovereign state in 1964. Although the country sits on an untold wealth of gems and minerals, it has not always been able to control and produce enough materials to meet demand. The early nationalization of mines in 1971 attempted to regulate the export of valuable resources, but inexperience and endemic crime impaired the fledgling market. The inconsistency of supply created large fluctuations in prices and discouraged many foreign businesses from investing in the uncertain environment. In an attempt to limit smuggling and keep more wealth within the country, Tanzania has implemented many new restrictions on the gem trade within its borders. At first banning the export of all rough gemstones across its borders, the country recently relaxed these laws to allow some rough to cross the border, but many regulations remain.

As the capital of the Ruvuma Region of Tanzania, Songea sits at an altitude of over 1000 meters. Like the rest of the country, this city of roughly 200,000 has a colorful history. Named after a great Ngoni chief who was executed following the Maji Maji rebellion in 1906, the region was later a restricted zone during the Mozambican Civil War. Today, however, the remote Tanzanian city is best known for its vibrant fancy sapphires.

First discovered in the early 1990s, the sapphires of Songea occur in a vivid rainbow of hues. In alluvial deposits along the tributaries of the Ruvuma River, striking green, purple, pink, orange, and yellow stones are found by artisanal small-scale miners. High levels of magnesium are thought to contribute to the broad range of fancy colors found in Songea, along with a high iron content. Though production from city’s mines has fluctuated with the discovery of new deposits nearby, these sapphires are back on the market once more, tempting buyers with their attractive colors.

One particularly special variety of sapphire can be found amongst the river gravels of Songea. These phenomenal gems appear one color in incandescent light, and an entirely different color under fluorescent light sources. This color change is not to be confused with color shift, as many gemstones may shift in color slightly in different lighting conditions, or pleochroism, where a stone shows variable colors depending on the viewing angle. Experts judge the color change phenomena on a scale from weak to moderate to strong, with the strongest color changes being the most prized. Color change is quite rare in sapphires, as it is caused by trace amounts of the element vanadium. As corundum seldom forms in areas with enough vanadium present to cause the phenomena, these exceptional specimens are highly desirable. The sapphires found in Songea can display truly astonishing color change that rival the famous alexandrite, with some fine rough appearing reddish purple in fluorescent lighting and violetish blue to green in natural light. Combined with impressive eye-visible pleochroism, these precious gems are veritable chameleons when cut.

Songea sapphire, songea sapphire rough, color change sapphire
Color change Songea sapphire rough

Both fancy colored and color change Songea sapphires are rising stars within the gemstone industry. With comparisons being made to the coveted fancy sapphires of Sri Lanka, the deposits in Songea offer a gorgeous range of hues in clean and nearly clean specimens, perfect for faceting. As Tanzania continues to refine its market and develop new gem centers in each of the country’s twenty regions, it is unclear what the future may hold for the supply of these beautiful gems. Those fortunate enough to acquire these stunning sapphires will possess an exceptional addition to their gemstone collection.