Cobalt Leaders

Cobalt production is heavily influenced by very large companies often focused on other mining sectors due to most of the world's cobalt being mined as a byproduct of large-scale copper or nickel operations.

According to the US Geological Survey (USGS), Idaho – where Century Cobalt's project is located – represents 1 of only 2 deposit locations in the US where primary cobalt production could occur (i.e., production not as a byproduct of another metal)

The top 5 cobalt producers

Glencore PLC | LSE:GLEN | Market Cap: $52.45B
Glencore is the world’s largest cobalt-mining company, with total production in 2017 of 27,400 tonnes, and plans to increase output to 63,000 tonnes by 2020. To grow its cobalt and copper presence, Glencore invested $960 million in 2017 to increase its stakes in 2 mining companies in the Democratic Republic of Congo (DRC).
China Molybdenum | HKEX:3993 | Market Cap: $34.06B
China Molybdenum, partially owned by the Chinese government, produced 9,314 tonnes of cobalt in 2016. The company paid $2.65 billion in 2017 to gain a stake in the Tenke Fungurume mine, which is located in the conflict-ridden DRC. According to traders, most of mine’s output is consumed by China.
Fleurette Group | Private
Fleurette produced a total of 7,595 tonnes of cobalt in 2016. Fleurette sold its stakes in 2 cobalt producing operations in the DRC – Mutanda Mining and Katanga Mining – to Glencore in 2017. The Fleurette Group of Companies has significant investment in diverse sectors, and substantial investments and operations in the Democratic Republic of Congo.
Vale | NYSE:VALE | Market Cap: $65.82B
Vale produced 5,811 tonnes of cobalt in 2017. The company produces cobalt as a byproduct in various mines in Canada producing mainly nickel, but also copper, cobalt, platinum-group metals (PGMs), gold and silver. Vale's attempts to sell its stake in a nickel/cobalt mine in New Caledonia have been thwarted due to technical issues, a chemical spill and violent protests by locals.
Gecamines | State-controlled
The Democratic Republic of Congo-controlled cobalt-mining company, Gecamines, produced 4,167 tonnes of cobalt in 2016. The company holds minority interests in a number of major DRC mines, with companies such as Glencore, US-based Freeport-McMoRan, and Canada’s Ivanhoe Mines holding controlling stakes and operating the projects.

Reference sources:
U.S. Geological Survey, Mineral Commodity Summaries, January 2018
Cobalt Investing News, Feb. 21, 2018
Vale website (production and sales in 4Q17)
Google Finance (market cap numbers)