Molycorp Facility Mountain Pass, CA Tour

Molycorp REE mine, Mountain Pass, CA

My graduate research at the University of California-Irvine centers on the aqueous separation of lanthanides/rare earth elements (a class of chemical elements).  Molycorp, Inc. is on the of the leading international mining companies of the rare earth elements, and they're located just three hours from school.

My graduate professor, Dr. Mikael Nilsson, our post-doc, Cory Hawkins, and I, along with a visiting professor from Japan, Prof. Masaki Ozawa Sensei, were privileged to receive a personal tour of the Mountain Pass Facility.  The plant manager showed us their facilities and explained the construction/technology upgrades implemented during the facility's 'Project Pheonix'.

For those who are not interested in any chemical or technical aspects of the tour, it was still an incredibly impressive feat in terms of shear volume of production. Millions of tons of dirt are removed by truckload up the sidled roads in the ore pit.  We walked the whole facility, from the ore mining (pictured above), to the end product, tens of 1-ton bags filled with purified rare earth minerals.  The bags are white and aligned in row after row in an enormous building, and look somewhat like pudgy snowman awaiting dispositioning in the hot CA weather.

Because it is currently on the forefront of my mind, I have to post a little snippet on the production facilities, which were operationally and chemically inspiring.

What does Mountain Pass mine?
The Mountain Pass area is of incredibly unique and bizarre geological composition.  The ore is mined for rare earth elements (REE).  REE use has skyrocketed due to it's use in high-technology applications: REE are in the magnets your cell phone, high energy efficiency lighting, and catalysts used in gasoline refineries.

 With respect to Mountain Pass, it is assumed that the dikes (or large strips of ore/earth that support mining) crystallized from primary magmas, derived directly from the earth's mantle without significant alteration or crustal interaction.  So, pretty  much a deposit high in REE concentration was extruded in magmatic form through the earth's crust, and sat for thousands of years without being bothered.  The strips of ore (called the Sulfide Queen stock) have ore grades as high as 15 percent REE, which is HIGH, at an availability of 20 million metric tons (at 5% cutoff grade).  For you chemistry geeks out there, the ore exhibits extreme preferential enrichment of light REE to heavy REE (Reference: it's cool, take the time to read it).  In short, Mountain Pass is a geological miracle.  I personally feel a sense of reverence, in a way, that the United States was blessed with an ore supply of elements and minerals that are so strategic in today's world.  The Lord has blessed this land, from it's very creation.

Crushing facility, where material is crushed and blended to the perfect specs.

What's the process?
A very basic flow of the Mountain Pass process is as follows.  Ore is mined from the pit (top picture).  At this point, the percentage of REE (or grade) of the ore is monitored.  This information is used as the ore is sent to a crushing milling facility (above picture).  As the ore is crushed, it is 'stacked' (see the mounds of dirt?) in such a way that if you were to take a big scoop at any location in the mound, the concentration of REE would be the same everywhere in the stack.  This is surprisingly important for downstream processing, and includes blending and downgrading where necessary.

The ore is then wetted goes through a flotation circuit to remove gangue.  A surfactant is added to the wetted ore, and binds with the REE.  The ore/surfactant mixture is put through an industrial-size Kitchenaid mixer (with a diameter of a backyard plastic swimming pool, with edges that are 5 feet high), and air is bubbled through the mixture up from the bottom.  The REE bubbles up and foams to the surface, where it spills over the edge of the floater, and is collected.  The rest of the material is heavy and doesn't bubble, and stays at the bottom.  Because, in general, the surfactant which supports bubbling is only attached to the REE, your overspill product is only REE. Chaching.

From here, you separate the REE from one another, which is the primary focus of my research.  That process, however, can't be disclosed.  Molycorp uses a secret, non-patented mixture, about which I'm only minimally informed.

The rock is captivating.

And for a last little nerdy treat- just outside the Mountain Pass facility is a decommissioned solar power plant, pictured below.  In essence, hundreds of mirrors are circularly arranged around a tower.  Molten salt (why molten salt? It can get hotter than water and is still remains a liquid) was pumped to the tip of the tower, and heated up by the directed concentration of sunlight (we're talking a thousand degrees).  The heated salt was run through a heat exchanged to generate steam, which is used to run a turbine and generate electricity.  Sunlight to electricity.

Solar Two facility outside of Mountain Pass