Mountain Pass

5 The location of the Mountain Pass deposit (orange balloon). Modified after Google Maps (2015). The city of Los Angeles in the center on the bottom of the map 

For a long time, the major ore deposit for rare earths was the Mountain Pass deposit, in California, USA (Fig. 2.5). 

The Molybdenum Corporation of America bought the rights to the ore bodies in February 1950. Later that year, the company started to sink a shaft (Hewett 1954). Many more veins with rare earth minerals were found in the surrounding hills. 

In 1950, J. C. Olson of the USGS and D.F. Hewett started to make a geological map of the area. They also found a large body of a carbonate type of rock, with relatively high amounts of barite (BaS04), about 20 %. The carbonate rock mass was called the Sulphide Queen carbonate body. Laboratory investigations showed 

6 Sovite. Alno alkaline and caibonatite ring complex, Sweden. From the collection of Naturalis Biodivtisity Center Leiden, The Nethcriands, Sample RGM387008.0. Photograph J.H. L. Voncken. Used with ptamission 

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Chandler D 1998 Finding transition pathways throwing ropes over rough mountain passes, in the dark Classical and Quantum Dynamics In Condensed Phase Simulations (Singapore World Scientific) pp 51-66... 

A geographical analogy can be a helpful way to illustrate many of the concepts we shall encounter in this chapter. In this analogy minimum points correspond to the bottom of valleys. A minimum may be described as being in a long and narrow valley or a flat and featureless plain. Saddle points correspond to mountain passes. We refer to algorithms taking steps uphill or downhill. ... 

Bastnasite has been identified in various locations on several continents. The largest recognized deposit occurs mixed with monazite and iron ores in a complex mineralization at Baiyunebo in Inner MongoHa, China. The mineral is obtained as a by-product of the iron ore mining. The other commercially viable bastnasite source is the Mountain Pass, California deposit where the average Ln oxide content of the ore is ca 9%. This U.S. deposit is the only resource in the world that is minded solely for its content of cerium and other lanthanides. 

Because of the importance of mass airflow rate in establishing engine output power, power available is sensitive to ambient conditions. Full-throttle engine power varies approximately inversely with inlet-air absolute temperature, but more significantly, approximately directly with ambient pressure. Mountain passes exist on public roads in the United States that have altitudes of over 12,000 ft. The normal atmospheric pressure at such altitudes results in a one-third loss in power capability in the typical passenger-car engine. 

The action of a catalyst can be explained in terms of our mountain pass analogy. In Figure 8-5 we see a formidable mountain pass obstruct-... 

This reaction describes a quasi equilibrium in the sense that it counts only those transition states moving forward (i.e., toward products) along the reaction coordinate. One can picture18 reactants moving along a potential energy surface such as that in Fig. 7-5. The transition state resides in one sense at the maximum of this surface in another sense, at the minimum point. This is called a saddle point or a col (from the French word for mountain pass). 

Personal experiences provide an intuitive sense of what energy is about. Backpackers climbing toward a mountain pass use energy to raise themselves and their packs up the mountain. When they reach the top, the hikers are tired after spending energy to make the climb. Scientifically, however, we need more than an intuitive sense of a concept as important as energy. 

In qualitative terms, the reaction proceeds via an activated complex, the transition state, located at the top of the energy barrier between reactants and products. Reacting molecules are activated to the transition state by collisions with surrounding molecules. Crossing the barrier is only possible in the forward direction. The reaction event is described by a single parameter, called the reaction coordinate, which is usually a vibration. The reaction can thus be visualized as a journey over a potential energy surface (a mountain landscape) where the transition state lies at the saddle point (the col of a mountain pass). 

Figure 2.35 (A) Flowsheet for heavy mineral processing in Thailand. (B) Flowsheet for processing bastnasite from mountain pass, California.

P. G. Bolhuis, D. Chandler, C. Dellago, and P. Geissler, Transition path sampling throwing ropes over mountain passes, in the dark, Arum. Rev. Phys. Chem. 53, 291 (2002). 

Another challenge is selecting an appropriate location for the turbine, due to the highly localized nature of wind. Low-cost anemometers may help alleviate this problem, but time must be spent to collect a sufficient amount of data [10]. Areas particularly suited to wind power because of their typical high wind velocities include coastlines, high ground, and mountain passes [12]. Wind power does not need water, so it is suitable for dry areas. 

This improvised explosive can be used for attacking bridge abutments, or causing a landslide to block a mountain pass, close a tunnel, derail a train, or similar purposes. 

Figure 6.3 Mountain pass or col analogy for the transition state.

The Mountain Pass (USA) operation treats a relatively complex ore. The major REO mineral is bastaenesite with minor amounts of synchisite, parasite and monazite. The major gangue minerals are calcite, barite, silicates, and dolomite. The amount of the individual gangue minerals in this ore are variable and change on a yearly basis. There are two major ore types treated at the Mountain Pass concentrator (a) high calcite ore (35-45% CaO) and (b) a high barite-dolomite ore (so-called brown ore). Barite also contains significant quantities of strontium. 

Liberation of the Mountain Pass ore has been extensively studied on the mill feed ore and on the plant product. Grinding the ore to a K 0 of about 56 pm is required to achieve liberation. Locking between the bastnaesite and calcite above 50 pm is common. Usually calcite/bastnaesite middlings reports to the final concentrate. 

The flowsheet used in the Mountain Pass, with reagent additions, is shown in Figure 24.7. The plant reagent scheme that is currently being used is presented in Table 24.3. 

It should be noted that the plant results are variable and depend on the type of ore being treated. Typical distributions of REO in the Mountain Pass concentrate are shown in Table 24.5. 

Reagent scheme used at the Mountain Pass concentrator... 

His body (see Figure 8.13) was retrieved and taken to the Department of Forensic Medicine at the University of Innsbruck. Their analytical tests - principally radiocarbon dating - suggest that Otzi died between 3360 and 3100 bc. Additional radiocarbon dating of wooden artifacts found near his body show how the site of his death was used as a mountain pass for millennia before and... 

An alternative and more costly approach is to actually follow the reaction from transition state to both the reactants and (independently) the products. In practice, this involves optimization subject to a fixed position along the reaction coordinate. A number of schemes for doing this have been proposed, and these are collectively termed Intrinsic Reaction Coordinate methods. Note, that no scheme is unique while the reactants, products and transition state are well defined points on the overall potential energy surface, there are an infinite number of pathways linking them together, just like there are an infinite number of pathways leading over a mountain pass. 

These materials are available through production of bastnasite at the Mountain Pass Mine in California, of monazite from Australia, India and Brazil, and of monazite as a by-product from the production of tin ores, rutile and various heavy mineral sands. 

Luckily, the U.S. has the largest bastnasite (R.E. fluocar-bonate) mine in the world located at Mountain Pass, California, owned and operated by Molycorp, Inc., a subsidiary of Union Oil... 

Current theories on their genesis revolve around a mechanism of mass gas transfer of material rich in carbonate derived from the upper mantle deep within the earth. The three most significant commercial carbonatite deposits are at Mountain Pass, California in the U.S.A., Palabora in South Africa and Paotou, Inner Mongolia in the Peoples Republic of China, see Figure 4. 

The Mountain Pass, California deposit now supplies nearly 100% of the world s bastnasite. Palabora deposits are mainly used for copper production but have given some rare earths concentrates in the past. The rare earths distribution in bastnasite, a fluoro-carbonate, is given in Table III. 

Fig. 1. Dry lake mineral bed near Mountain Pass, California contains over one million pounds of neodymium and nearly one-half million pounds of praseodymium, bo til elements once regarded as rare earths" and of limited scientific curiosity. During recent years, die rare earths have become significant materials in the electronic, chemical, metallurgical, glass, cryogenic, nuclear, and ceramic refractory industries. Lanthanum, another rare-earth element, is more abundant than lead...

Until 1964, monazite, a thorium-rare-earth phosphate, REPO4TI13 (P04)4, was the main source for the rare-earth elements. Australia, India, Brazil. Malaysia, and the United Slates are active sources. India and Brazil supply a mixed rare-earth chloride compound after thorium is removed chemically from monazite. Bastnasite, a rare-earth fluocarbonate mineral REFCO3. is a primary source for light rare earths. From 1965 to about 1985. an open-pit resource at Mountain Pass, California, has furnished about two-thirds of world requirements for rare-earth oxides. In the early... 

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