Prices for cobalt , a key ingredient in lithium-ion batteries for electric vehicles, have spiked 83 percent this year on forecasts that demand will double in the next decade as consumers switch to less-polluting cars.

Nearly all cobalt, which prolongs battery life, is mined as a by-product of copper and nickel, making it difficult for investors to get direct exposure.

Much like the recent boom in lithium, another battery ingredient, cobalt's surge has resulted from heady forecasts for ownership of electric vehicles. UBS in May said it expected them to account for 3.1 percent of global car sales in 2021 and 13.7 percent in 2025, up from 1 percent this year.

In response, small cobalt-focused companies are mushrooming, mostly in Canada, a long-time hub for mining start-ups, but only one, Cobalt 27 Capital Corp (>> Cobalt 27 Capital Corp), concentrates entirely on the mineral.

"To gain exposure to the cobalt theme in any pure way, you almost have to go down the market capitalization spectrum," said portfolio manager Ben Cleary of Sydney-based Tribeca Investment Partners.

Institutions are often wary of small-cap stocks, which can be volatile and difficult to sell because of their small number of investors.

Tribeca, which manages A$2.5 billion ($2 billion), owns shares of Canada's Ecobalt Solutions Inc (>> Ecobalt Solutions Inc), which is building a cobalt mine in Idaho. It also has stock in small Australian miner Cobalt One (>> Cobalt One Ltd), which is being acquired by Canada's First Cobalt in a three-way tie up to expand its exploration land in the province of Ontario.

COBALT LISTINGS SURGE

At the end of July, 110 companies mining or exploring for cobalt were on the Toronto Stock Exchange and TSX Venture Exchange, a market for smaller-capitalization stocks, compared with fewer than 30 in 2015, according to SNL Financial.

Some of the optimism is already built into cobalt stocks. Cobalt One has surged 30 percent this year, First Cobalt has nearly doubled, and Ecobalt has jumped 144 percent.

Some junior miners point out that their projects are in more politically stable regions than the Democratic Republic of Congo, where more than half the world's cobalt is produced. Last year Amnesty International said some mines there were using child labor.

"(Tesla Inc (>> Tesla) Chief Executive Officer) Elon Musk and others are saying: 'Where do I get my cobalt if I don't want to go to the Congo?'" said First Cobalt CEO Trent Mell.

Tesla has said it would like to source raw materials for its "Gigafactory" battery plant in North America.

At least two more cobalt explorers with Ontario projects are planning listings on the Toronto Stock Exchange in coming months, an industry source said, requesting anonymity because the information is not public.

That would follow the June listing of Cobalt 27, which raised C$200 million ($159.21 million) in the market's biggest mining initial public offering since 2012.

BlackRock Inc (>> BlackRock), the world's largest asset manager, bought Cobalt 27 shares, it said in a June 30 securities filing.

Cobalt 27, which owns about 2,200 tonnes of cobalt and is not a miner or explorer, was created specifically to give institutions direct access to investing in the metal without the exploration and development risks facing miners, said CEO Anthony Milewski.

"It is really the only pure play that exists," Milewski said.

($1 = 1.2661 Australian dollars)

($1 = 1.2562 Canadian dollars)

(Reporting by Nicole Mordant in Vancouver; Editing by Lisa Von Ahn)

By Nicole Mordant