The venture aims to help companies find the best prices on everything from drilling equipment to dynamite.
The founding companies say the marketplace will take a bite of the industry's annual $200 billion spending bill. The companies represent 60 percent of the global mining and metals market and include the world's largest producers of aluminum, copper, gold, platinum and iron ore.
Backers will invest up to $100 million in the project as it prepares for an eventual initial public offering.
It is expected to start Net-based transactions by the end of the year.
This is the second online purchasing site for the metals industry to be unveiled in as many weeks. Earlier this month, eight metals companies including Alcoa unveiled MetalSpectrum, an online marketplace targeting the specialty metals industry such as platinum and aluminum. This site is expected to be running in September.
Last week, four European steel manufacturers said they are building a marketplace for the industry. The steel producers have hired U.S. consulting firm Andersen Consulting to help define the market's commercial strategy and management.