The last major elements of the $1.5 billion expansion and modernization of Molycorp Inc.’s rare earth mining and processing facility in Mountain Pass, Calif., are done, according to the company.

Specifically, the mine’s chloralkali plant is “mechanically complete” and work to start up the plant has begun, the Greenwood Village-based mining company (NYSE: MCP) said Wednesday.

Also, the last unit of the mine’s “multi-stage cracking plant” also is mechanically complete and startup procedures have begun, Molycorp said.

"This means that the final construction work on the $1.5 billion rebuild of the Mountain Pass facility is complete,” Molycorp’s spokesman, Jim Sims, told me. “The units are now in commissioning and following that they’ll go into full-scale production,” he said.

Molycorp mines rare-earth elements, which are processed into compounds vital for a number of industrial and military applications, including electronics, oil refining, bombs and special magnets used in wind turbines and electric cars. At Mountain Pass, Molycorp owns the biggest U.S. deposits of rare earths.

The chloralkali plant takes wastewater from the process that separates mining ore and the rare earth elements and recycles it into feedstocks for the separation process, Sims said.

"It greatly reduces the environmental footprint at Mountain Pass, and it also drives down our production costs,” Sims said. Molycorp hopes its process will be competitive with the lowest cost rare earth producers in the world, the company said.

The mine’s multi-stage cracking plant is part of a chemical process that raises the amount of rare earth elements the facility can get from the ore, speed up the production process, and also lower costs, the company said.