There is such a metal, which has a wide range of uses in aviation, aerospace, machinery, automobiles and other fields, especially in the military field, and is known as "war metal". Unfortunately, for more than 100 years, the total production of this metal in the world is only a few tons, what is it?
People love molybdenum lead ore
“Wulfenite is Loved!” This is the theme of the 65th Tucson Gem and Mineral Exhibition in the United States in 2019, if translated as Chinese, it means "everyone loves molybdenum lead ore".
The Tucson Gem and Mineral Exhibition is a world-renowned gem and mineral thematic exhibition that attracts gem and mineral enthusiasts from all over the world every year. Being chosen as the protagonist of this exhibition and accompanied by such advertising slogans shows that molybdenum lead ore is by no means an "idle person".
The theme of the 65th Tucson Gem and Minerals Exhibition 2019 is molybdenum lead ore
Molybdenum lead ore is a lead molybdenate mineral with the chemical formula Pb [MoO4], the most common is a flake crystal, with a greasy luster or diamond luster, the color is mostly red, orange, yellow or brown, transparent to translucent. The redness of color is due to the composition of tungsten contained in it. The orange-red color of molybdenum lead ore is particularly brilliant, this crystal is not a strong point in terms of crystal form and combination form, but the strong and fiery color makes up for the lack of form, and the color (including luster) is the soul of molybdenum lead ore.
Molybdenum lead ore is also sometimes referred to as "yellow lead ore" or "color molybdenum lead ore". It is often symbiotic with quartz, calcite, vanadium lead ore, chromium lead ore, white lead ore, phosphate chloride lead ore and other minerals, mainly produced in the oxidation belt of lead and zinc deposits, is a secondary mineral, so the place where molybdenum lead ore is formed is often famous for large lead and zinc deposits, especially in the arid desert, in addition to arizona in the United States, Mexico, Namibia, Iran, Australia, Morocco and other countries also have molybdenum lead minerals, molybdenum lead ore has been found in Ruoqiang County, Xinjiang, the mainland.
Molybdenum lead ore encyclopedia
【Chemical Composition】
Pb [MoO4], of which PbO accounts for about 60% and MoO3 accounts for about 40%, sometimes containing W, V, Ca, TR, etc.
【Crystal characteristics】
It belongs to the tetragonal crystal system, tetragonal bipyramiform crystal class, and has almost equal shaft ratios, which is crystallographically similar to white tungsten ore (CaWO4). Crystals are more likely to be plate-like and flake-like, and a few are cone-shaped and columnar.
Island structure of colmolybdenum lead ore
Color molybdenum lead ore crystals
【Physical Properties】
Hardness: 2.5-3 (nails can not be scratched, knives can be scratched)
Specific gravity: 6.5-7g/cm³
Cleavage: Clear angular conical cleavage
Fracture: Shell-shaped fracture
Color: yellow, waxy yellow, straw yellow, orange yellow to orange red (the color red is mainly containing W)
Streaks: yellowish-white
Transparency: Transparent to translucent
Gloss: Grease gloss or diamond luster
【Identification characteristics】
Molybdenum lead ore can be identified from square plate-like, orange to yellow, diamond luster, high density and other characteristics of lead mineral symbiosis.
【Causes】
It is mostly found in the oxidation belt of lead and zinc deposits, and it is often described as white lead ore.
Treasure Hunter's "Desert Flower"
In the 1860s, Spanish geologists discovered a silver area in the desert north of Yuma, Arizona, and named it The Red Cloud Mine. The mine has not only silver, but also lead. The miners first mined in the open pit, then dug the roadway and went underground to find the ore vein. However, due to the backwardness of mining technology, although it lasted for two or three decades, the profit was less than one million US dollars. Later, as silver prices fell, the Red Cloud Mine was forced to stop production.
It is said that miners often find a bright, thick leaf-like red mineral when mining, which is crystal clear and brightly colored. However, the miners did not feel that this red "stone" had any special use, and most of them casually threw it into the minecart and sent it into the smelter.
The speaker has no intention, the listener intends. Word reached the ears of mineral collectors, who traveled to the Red Cloud Mine in search of specimens of the mineral. Even decades after the Red Cloud Mine closed, treasure hunters continue to flock. Today, there are many museums around the world that preserve specimens from the Red Cloud Mine, known as the "Flower of the Desert".
In fact, this mineral was first discovered by the Austrian mineralogist F.X. Wulfen in Bad Breberg, Carinthia, Austria, and was subsequently named wulfenite after him, which translates to Chinese is molybdenum lead ore.
Franz Xaver von Wulfen
"War metal" in the military field
Molybdenum lead ore contains not only lead, but also another very important metal element - molybdenum. The amount of molybdenum on Earth is small and more dispersed, and it belongs to rare metal elements. In addition, molybdenum does not exist in elemental form, but mainly combines with sulfur to form a compound to form molybdenite (chemical formula MoS2); or combined with lead to form molybdenum lead ore.
Molybdenum is a silvery-white metal with a hard texture and a melting point of up to 2623 ° C, ranking sixth after the natural elements carbon, tungsten, rhenium, osmium and tantalum. The addition of molybdenum to steel to make an alloy can not only improve the corrosion resistance of steel, so that it has good thermal conductivity and a small coefficient of expansion; moreover, this alloy still has high strength under high temperature conditions. Therefore, molybdenum is mainly used in the manufacture of alloys, and has a wide range of uses in aviation, aerospace, machinery, automobiles and other fields, especially in the military field, which is of great significance and is known as "war metal".
From 1781, when scientists first isolated molybdenum from the compounds of the ore, for more than 100 years, the total production of molybdenum metal in the world was only a few tons.
With the outbreak of the two world wars, the performance requirements of various countries for weapons and equipment have been continuously improved, and the importance of molybdenum has gradually emerged, and its output has gradually increased. During the "First World War", a certain British tank was equipped with a 75 mm thick manganese steel plate on the body in order to enhance its offensive performance while strengthening its own protection; however, this bulky tank did not perform well in the war. Later, through experimentation, the British replaced the manganese steel plate with molybdenum steel plate, and the thickness was reduced to 25 mm, which not only greatly reduced the weight of the body, the tank became more maneuverable and flexible, but also increased the tank's ability to resist blows.
Theoretically, molybdenum lead ore contains about 26.1% molybdenum, so people used molybdenum lead ore to smelt metal molybdenum in the early days. However, smelting molybdenum with molybdenite is easier and cheaper, so the industrial value of molybdenum lead ore is not as important as molybdenite. Molybdenum ore is not proud, looks black, and is very similar to graphite; molybdenum lead ore is exceptionally beautiful, "appearance" is far better than molybdenum ore, so it gradually entered the collector's field of vision.
A "work of art" that can only be viewed from a distance
Molybdenum lead ore from different origins has its own advantages and unique characteristics. The molybdenum lead mine in the Red Cloud Mine in Arizona, usa, is known for its deep red color, the Mexican production is mainly orange, and the Molybdenum lead mine in Slovenia is yellow... It is precisely because of their bright colors and beautiful shapes that they often become the object of artistic creation.
The postal services of many countries are fond of molybdenum and lead mines. Data show that to date, at least 30 countries around the world have issued stamps with molybdenum-lead ore as the theme, such as the Republic of Djibouti in northeast Africa in 2015 issued a stamp with molybdenum lead ore crystals, with a face value of 300 Djiboutian francs, which is collected by many people.
Molybdenum lead mine stamp issued by the Republic of Djibouti in 2015
Geologists have found that the lead (Pb) in molybdenum lead ore can be partially replaced by calcium (Ca) and molybdenum (Mo) can be partially replaced by tungsten (W), so the crystal structure of molybdenum lead ore and white tungsten ore (CawO4) is very similar, but its crystals are usually thinner and flatter than white tungsten ore. People who like to collect white tungsten ore know that white tungsten ore has a strong "fire", molybdenum lead ore is better in this regard, transparent molybdenum lead ore has a high refractive index (2.283 ~ 2.405) and dispersion (0.203) to light. If properly cut, molybdenum lead ore can exhibit a "fire" phenomenon like a diamond.
However, molybdenum lead ore is too fragile, and its Mohs hardness is only 2.5 to 3. This means that it is only slightly harder than the fingernails, which is very inconvenient to process, and it will be damaged if you are not careful. Therefore, molybdenum lead ore did not appear in the jewelry market, but only for some museums or private collectors. The prestigious Gemological Institute of America houses a gem-like cut molybdenum lead ore, weighing 21.5 carats, from Chumeb, Namibia. This molybdenum lead ore is dazzling and shining, but it can only be viewed from a distance and cannot be blasphemed", which is inevitably regrettable.
Molybdenum lead ore picture appreciation
Source: Institute of Geology and Geosciences, Chinese Academy of Sciences, Encyclopedia of Knowledge