They have quite a diverse range of products that they specialise in, however, their biggest exports are gold. Since gold is a natural resource, it is very unreliable so if it were to be completely depleted, a major part of the economy would be affected.
Gold Prices in Singapore Dollars for the past 5 years
Gold prices are very volatile, therefore, having your major export be in such a product is very risky. Prices have dropped significantly from March of 2012 to March of 2017. No one knows for sure where the next big turn will take therefore the future of Tanzania looks very risky.
Access international markets: Tanzania has a relatively low access into the international market because it's imports costs $13.5 billion while their exports only bring in the revenue of $6.4 billion. This is because they have insufficient access into the international market to be exporting to therefore, they do not get much revenue. The gold market is a huge industry with countries who produce gold more efficient and cheap therefore, not making Tanzania their first option. Moreover, since appropriate technology is not that visible for the industry therefore the quality of the gold is also not the best. Tanzania is not even in the top 14 gold producing countries in the world. Tanzania only produces 40 metric tonnes while China produces over 450 metric tonnes.