Although a rare mineral, coltan is found in many countries throughout the world. Extracting it is not difficult, and exploratory coltan mines are quite common. But not all of the countries that extract it do so ethically. The products that come from this extraction are a crucial component of many modern electronics, particularly phones, DVD players, many video gaming systems, and some of the most modern computers. The mineral itself is a mixture of columbite and tantalite, from which niobium and tantalum can eventually be obtained. These are then used in the most sensitive electronics.
Sites already exist in Australia, Brazil, Canada, the Democratic Republic of Congo, China, Ethiopia, and Mozambique. Among those, the most ethical are considered to be Australia, Brazil, and Canada. Most of the others suffer from poor regulation and oversight, which potentially leaves the workers open to dangerous abuses.
However, in no location is this danger so pronounced as the Democratic Republic of Congo. Long notorious for "conflict diamonds" produced for Western consumption at the expense of totally unsupervised workers in horrible conditions, the local mineral operations are much the same.
For this reason, a number of companies refuse to purchase from the DRC, China, Ethiopia, and Mozambique. Considering the availability from other sources and the much more ethical methods used there, no real reason exists to use anything from conflict coltan mines.
With the increasing demand for the minerals it's no surprise that new locations are constantly being explored. Current expeditions are evaluating sites in Saudi Arabia, Egypt, Uganda, Greenland, the US, Finland, and Afghanistan. Of this group, only a handful seem to have the necessary infrastructure to support refinement, storage, and move the product successfully while also keeping an eye on workers.
The minerals found directly in the ground are not useful in their raw, unrefined state. They will be taken out and further separated into their components, which are then eventually used for electronics manufacturing. It is common for companies to extract the ore in one location, ship it to another, refine and/or package it there, and then move it onward to its final destination. For this reason it is not guaranteed that you will find a packaging and storage plant in the same location as the actual point of extraction. It will usually be nearby to facilitate faster shipments, but it isn't guaranteed to be in the same country. As a result, it's important to always ask where the product comes from directly.
The areas where coltan mines can be found are very diverse. There is not a lot of obvious geological similarity between Greenland and Egypt or Canada and the Democratic Republic of Congo. The answer is not particularly simple. Few scientists have devoted their time to researching the geologic underpinnings of this important natural resource. Most of the energy from the academic world, journalists, and the more scrupulous producers alike is devoted almost entirely to bringing the abuses present in the DRC and elsewhere into the popular consciousness. What is clear, however, is that the prevalence of these deposits around the world has only just started to become evident. It is quite likely that more will be discovered in the future.