Unique to Tanzania, supplies of tanzanite are limited and demand is rising as Kilimanjaro's foothills continue to produce this rare stone.

After nearly a year of negotiation, the government and mining giant TanzaniteOne have reached an agreement regarding the future of tanzanite mining in the country. According to the deal, the State Mining Corporation (STAMICO) will own a 50% stake in TanzaniteOne, a subsidiary of Richland Resources. Following a letter of intent drafted in early 2013, a conclusion to the deal was sealed in May.

Having lifted a ban on the export of the rare minerals in 2010, the Tanzanian government has been working to curb smuggling and illegal mining operations. Through the joint venture, STAMICO and TanzaniteOne can work together to implement and enforce the regulations necessary to boost and protect trade. The partnership will also facilitate the mining of the gem, as mining operations will be conducted in a collaborative and safe environment.

The global wholesale market for tanzanite is valued at approximately $300 million per year, and the gem itself is worth between $700 and $1,200 per carat in the US. However, once a faceted tanzanite gemstone is set into jewelry, the cost of tanzanite can rise to between $2,000 and $3,200 per carat for top-quality gems. Of total sales abroad, the Tanzanian government rakes in approximately $20 million per annum.

The tanzanite-producing area of the country is roughly 8 square kilometers in size—2 kilometers wide and 4 kilometers long—and is divided into four blocks. Of those, TanzaniteOne owns the largest, with the remaining areas operated by smaller, local, or artisanal miners. While the company's annual production figure hovers in the mid-30,000-ton range, TanzaniteOne's ore treatment plant has the capacity to process 10,000 tons of tanzanite per month.

Tanzanite is one of the world's scarcest gems, 1,000 times rarer than diamonds. Dubbed for the one country it has been discovered in, tanzanite has been mined in the foothills of Africa's tallest mountain, Kilimanjaro, since the late 1960s. Due to the rare geological phenomenon that created tanzanite, experts predict that the chances of tanzanite being found somewhere else or formed again are less than a million to one, meaning that the total supply of the gem is expected to be exhausted within the current decade.

The gem's three colors—often appearing as sapphire, violet, and burgundy—are what make it popular with jewelers and buyers, especially for use in necklaces, earrings, or bracelets. In addition, the color of tanzanite changes depending on lighting conditions, with fluorescent light and incandescent light reflecting its blue and violet shades differently. These qualities have led it to gain recognition as a December birthstone, the only gem to be added to the calendar after the current list was drafted in 1912.

One of the most famous tanzanite samples is a 242-carat stone, fondly called the “Queen of Kilimanjaro." The gem was set in a tiara and accented with 803 tsavorite garnets and 913 diamonds. Currently, the stone is part of the private collection of Michael Scott, Apple's first CEO. Another famous stone was discovered 2005, and, at 16,839 carats and 3.5 kilograms, it is the largest tanzanite crystal in the world.

As its popularity and rarity increases, tanzanite is considered a suitable investment for collectors and speculators alike. Although its value decreased marginally in 2012, the price-per-carat of tanzanite has steadily risen over time, and gemologists expect this trend to continue as new supplies continue to dwindle.