Currently, most beryllium (93% of world output in 2000) comes from a bertrandite deposit in Juab County, Utah, in Spor Mountain. Bertrandite is Be4Si2O7(OH)2, an alteration product of beryl. It forms clear or white orthorhombic crystals with one plane of good cleavage, is hard (6-7) and of moderate weight (sp.gr. 3.3-3.5; one source says 2.6). The concentrate is sent to Ohio for processing.

Perhaps the most important beryllium mineral after beryl and bertrandite is chrysoberyl, Be(AlO2)2, which at 8.5 is nearly as hard as corundum. Its crystals are orthorhombic, often occurring in pseudo-hexagonal clusters. When of gem quality, chrysoberyl provides alexandrite, with its amazing dichroism, that makes it red when seen from one direction, green from another, and also cat's eye, with inclusions of rutile (TiO2). Another rare beryllium mineral is euclase, named after its perfect cleavage. Its formula is BeAlSiO4(OH). It is a phyllosilicate (layered, like mica; beryl is a 3D tectosilicate), found in granite pegmatites, often with topaz. Due to its hardness (7.5) and durability, it is also found in placers. It may be clear, green or blue.

Nuclear Properties

The atomic number of Be is only 4, and the only naturally occurring isotope has mass number 9, so the nucleus contains 4 protons and 5 neutrons. The atomic weight is 9.012. The isotope with mass number 8, which might be expected to be quite stable with paired-off protons and neutrons, actually splits with a half-life of less than 4 x 10-16 seconds into two alpha particles, which are even more stable. The decay energy is only 90 keV, however. Be8 is the only light nuclide to undergo alpha decay, but it is a very unusual sort of alpha-decay, that is also fission at the same time. Be7 captures an orbital electron (K-capture) to become Li7, half-life 53 days. Be10 is nearly stable, since its half-life is 2 x 106 years against beta-decay to stable B10. These are the only four beryllium nuclides.

Beryllium played an important role in the discovery of the neutron. The nuclear reactions that occurred when fast alpha-particles collided with light nuclei were extensively studied. The (α,p) [alpha in, proton out] reaction was an example, as in N14(α,p)O17. The reaction with Be9 produced a very penetrating radiation, very unlike a fast proton, that was initially believed to be a gamma ray (photon). However, in 1932 Chadwick showed that it was an uncharged massive particle that could eject protons by collision, which a gamma could never do. The reaction was, in fact, Be9(α,n)C12. This solved the outstanding problem of the constitution of the nucleus, since everything was consistent with an assembly of Z protons and A - Z neutrons, all with half-integral spin.

The thermal neutron absorption cross section of Be9 is only 10 mbarns, a rather small value, so beryllium makes a good neutron moderator in fission reactors. It is lighter than C (9 vs. 12), so a neutron can lose more energy in one collision with beryllium that with carbon. Neutron absorption reactions are Be9(n,α)He6 (winding up as Li6), and Be9(n,2n)Be8 (winding up as 2α). Beryllium is not only a moderator, but also a source of neutrons. Beryllium was considered a promising material for high-temperature nuclear reactors (carbon, of course, cannot be used). Beryllium was used as a neutron reflector to reduce the size of reactor cores. It is used in nuclear weapons for the same purpose.

Metallurgy

Beryllium ores contain no more than 5% Be, because it is so light. The first step is to decompose the beryl, and separate the beryllium. This can be done with hydrofluoric acid or fluorides, producing a soluble fluoberyllate such as BeF2·2KF. Sulphates or chlorides can also be formed. Beryllium can then be precipitated as the hydroxide Be(OH)2, which on heating gives BeO. BeO, beryllia, is a very useful ceramic with a melting point of 2570°C and great resistance to thermal shock.

The metal can be produced by electrolysis at temperatures just below its melting point, or about 1300°C. Unlike most metallic halides, BeCl2 is poorly conducting when fused, so it is usually mixed with NaCl. Barium and sodium fluorides, in which BeO or BeF2 are dissolved, can also be electrolyzed. The metal is obtained in fine flakes or globules, and considerable processing is necessary to remove the slag. BeO can be reduced by carbon, but the product is the carbide, Be2C. Currently, the preferred method is reducing BeF2 by magnesium metal. In general, the metallurgy of beryllium is very difficult.

Beryllium and beryllium oxide in any forms are quite expensive, and this fact limits their use. The current price (2004) for the powder metal is $375 per pound, and for copper master alloy, $160 per pound of Be content.

Properties and Uses

Beryllium crystallizes in the hexagonal close packed structure. It is definitely a metal, but a hard and brittle one. Its electron configuration is 1s22s2, so its compounds can be expected to be electron-poor and somewhat exotic. It is a rather small ion, of radius 0.31Å. Its ionic valence is clearly 2, and this is shown in numerous compounds. The first ionizing potential is 9.28V, greater even than that of magnesium. In the halides, the electron transfer is not by any means complete, and these compounds do not ionize easily. The compounds of beryllium are colorless. Aside from these properties, beryllium behaves similarly to aluminium. It is not much like magnesium, calcium or barium, the other elements called the alkaline earths, except in valence. In fact, it is not very alkaline at all, and its oxide and hydroxide are not even soluble. It is not mentioned in qualtitative analysis texts, since it is encountered very rarely. It probably is separated with the aluminium and must then be distinguished from it by the precipitation of a basic carbonate by adding ammonium carbonate. An excess of reagent dissolves the precipitate. Like aluminum, it forms a protective oxide layer on exposure to air, which makes the surface very hard. Beryllium resists atmospheric corrosion at high temperatures better than titanium or zirconium. Above 600°C, the oxide is first formed, and then the nitride, Be3N2 at 1000°C. Metallic beryllium should not be used at temperatures over 600°C.

The specific gravity is 1.85, only slightly greater than that of magnesium (1.74) and considerably less than that of aluminium (2.7). Its hardness is 6.5, melting point 1285°C, boiling point 2780°C. It would be an exellent light, strong structural material for high temperatures if it were not for its brittleness and extreme difficulty of working. Its electrical resistivity is 18.5 μΩ-cm, a relatively low value, making it useful for electrical leads. The thermal expansion coefficient is 12.3 x 10-6 °C-1, heat capacity 0.425 cal/g/°C and heat conductivity 0.3847 cal/s/cm2/°C/cm. The latent heat of fusion is 341 cal/g.

As a sintered powder (1000°C, 500 psi), the ultimate strength is 45,000 psi, yield point 25,000 psi, Young's modulus 44 x 106 psi, and Poisson's ratio 0.024 (? this seems a very small value). The high Young's modulus and low density make the speed of sound in beryllium quite large (12,500 m/s). The elongation of a tensile specimen on fracture is only around 2%, so the ductility is low. Impact strength is also low. Hot-pressed beryllium can be succesfully machined and drilled. Beryllium can also be vacuum cast, but it is very difficult to machine the castings. Beryllium can be forged hot if encased in steel, and it can be welded, but must be protected from the air.

The alloy 97.75 Cu, 2.25 Be has six times the strength of copper. It is nonsparking (chips do not oxidize readily in air), nonmagnetic, and does not exhibit fatigue failure. Similar alloys may have from 2% to 3% beryllium. This material makes excellent springs, and is a good electrical conductor, since the resistivity of the copper is not raised excessively by the beryllium. Beryllium for alloying is supplied as a 4% alloy with copper, called "master alloy." Since little beryllium is used, its high cost is a minor factor. Be-Al alloys, with up to 65% Be, are also being studied. Phosphor bronze is a substitute for beryllium copper, but is not as serviceable. The Chemical Society's internet periodic table says beryllium is used "to increase the ability to conduct electricity" in copper and nickel, but this is erroneous. Beryllium improves the mechanical properties of the metals, but does not increase the resistivity as much as other alloying elements.

Beryllium and its compounds are very poisonous, especially as dusts. When inhaled, they can produce beryllosis, which is like silicosis, and destroys the lungs. Although some people are little affected, others can develop a sensititivity to beryllium called chronic beryllium disease that scars the lungs. Carcinoma can also result from beryllium poisoning. It is chilling to think that glucinium was named because of the sweet taste of its compounds; its poisonous nature was probably verified at the same time. BeO was used as a phosphor in fluorescent lamps, which made broken discarded fluorescent lamps a great hazard. I understand that BeO phosphor is no longer used. This is much more of a hazard than mercury in refuse. Atomic weapons workers are also subject to beryllium poisoning, although great care has been taken to eliminate the hazard. It is easy to blame beryllium for any lung problems that occur with these workers whatever the cause, to the great delight of lawyers. Beryllium copper and similar uses of the metal, or of beryllia, are not hazardous. There is very little beryllium in the environment, and no evidence that trace amounts are dangerous. The EPA limit is 0.01 μg/m3

in air, the OSHA limit 2 μg/m3 for an 8-hour shift. Beryllium dust from burning coal is a negligible hazard, because of the very small amounts involved.

Because of its low atomic number, beryllium is nearly transparent to X-rays and can be used as windows for X-ray tubes. Currently, the greatest demand for beryllium comes from the telecommunications equipment industry.

References

F. X. M. Zippe, Geschichte der Metalle (Wien: Wilhelm Braumüller, 1857). pp. 358-360.

J. L. Bray, Non-Ferrous Production Metallurgy, 2nd ed. (New York: John Wiley

C. H. Hurlbut, Jr., Dana's Manual of Mineralogy, 16th ed. (New York: John Wiley

W. N. Jones, Jr., Inorganic Chemistry (Philadelphia: Blakiston, 1949). pp. 607-609.

S. Glasstone and A. Sesonske, Nuclear Reactor Engineering (New York: Van Nostrand Reinhold Co., 1967). pp. 442-445.

For the latest data on beryllium, see Roskill. For toxicity information, see ATSDR.

The Occupational Safety and Health Administration (OSHA) has recently obtained information suggesting that OSHA's current 2 micrograms per cubic meter of air (micrograms/m3) eight-hour time-weighted average (TWA) permissible exposure limit (PEL) for beryllium in the workplace may not be adequate to prevent the occurrence of chronic beryllium disease (CBD), a disabling and often fatal lung disease, among exposed workers.

OSHA is publishing this Hazard Information Bulletin to alert employees working with beryllium about the hazards associated with their work. It describes engineering controls, work practices, and personal protective equipment recommended for controlling exposures to beryllium through inhalation and skin contact. It also suggests health surveillance methods to identify workers who may have become sensitized to beryllium, or who may have CBD.

Background

Beryllium is a metal that is found in nature, especially in beryl and bertrandite rock. It is extremely lightweight and hard, is a good conductor of electricity and heat, and is non-magnetic. These properties make beryllium suitable for many industrial uses, including: metal working (pure beryllium, copper and aluminum alloys, jet brake pads, aerospace components); ceramic manufacturing (semi-conductor chips, ignition modules, crucibles, jet engine blades, rocket covers); electronic applications (transistors, heat sinks, x-ray windows); atomic energy applications (heat shields, nuclear reactors, nuclear weapons); laboratory work (research and development, metallurgy, chemistry); extraction (ore and scrap metal); and dental alloys (crowns, bridges, dental plates); and sporting goods (golf clubs, bicycle frames).

Current Exposure Limits

The current OSHA PELs for beryllium are 2 micrograms/m3 as an 8-hour TWA, 5 micrograms/m3as a ceiling not to be exceeded for more than 30 minutes at a time, and 25 micrograms/m3as a peak exposure never to be exceeded. The OSHA limits have been in place for nearly 30 years and have not been revised in that time. The American Conference of Governmental Industrial Hygienists (ACGIH) has recently published a Notice of Intended Change for its Threshold Limit Value (TLV) for beryllium that would lower the TLV from the current level of 2 micrograms/m3 to 0.2 micrograms/m3averaged over an 8-hour work shift.

Potential Adverse Health Effects From Beryllium Exposure

Chronic Beryllium Disease

Chronic beryllium disease (CBD) primarily affects the lungs. CBD may occur among people who are exposed to the dust or fumes from beryllium metal, metal oxides, alloys, ceramics or salts. It occurs when people inhale beryllium in these forms. CBD usually has a very slow onset, and even very small amounts of exposure to beryllium can cause the disease in some people. In some cases, CBD develops while workers are still on the job, but in others it may not develop until many years after a person has stopped working in the beryllium industry, or has been transferred to a job that does not involve beryllium exposure. The amount or length of exposure to beryllium necessary to cause a specific individual to develop CBD is not known, but recent information suggests that exposure below OSHA's 2 micrograms/m3 TWA PEL over a very short time (weeks or months) can lead to CBD in some workers.

Signs and Symptoms of Chronic Beryllium Disease

Workers with advanced CBD may have one or more of the following symptoms: unexplained cough; shortness of breath, especially with activity; fatigue; weight loss or loss of appetite; fever; or night sweats. However, because the disease may develop slowly over a period of many years, workers may have the disease for a long time without knowing it.

Beryllium Sensitization

CBD only develops in workers who have become sensitized to beryllium. A sensitized worker is one who has developed an allergic reaction to beryllium. A worker may become sensitized at any point during job exposure, or in some cases may not become sensitized until after leaving a job where there has been beryllium exposure. Beryllium sensitization can be detected through the use of a blood test called the BeLPT, which stands for beryllium lymphocyte proliferation test. This test measures how specific white blood cells called lymphocytes react to beryllium. A positive test result means that a worker is sensitized.

Acute Beryllium Disease

Acute beryllium disease usually has a quick onset and has symptoms that resemble those of pneumonia or bronchitis. The acute form of the disease is believed to occur as a result of exposures well above the current PEL. This form of beryllium disease is now rare.

Cancer

Studies of workers exposed to beryllium have demonstrated significantly elevated risks of lung cancer. The International Agency for Research on Cancer (IARC), the expert cancer agency of the World Health Organization, has concluded that exposure to beryllium can cause lung cancer in humans.

Skin disease

A skin disease, which is characterized by poor wound healing and a rash or wart-like bumps, can occur as a result of the skin being exposed to beryllium dust.

Recommendations

OSHA recommends the following measures to reduce exposure to beryllium in the workplace and to determine whether workers have beryllium sensitization or CBD.

1. Engineering Controls

Employers should use appropriate engineering controls and work practices to ensure that worker exposures to beryllium are maintained below the current OSHA PELs to the extent feasible. The following engineering controls and practices should be used by employers:

* enclose processes;

* design and install appropriate local exhaust ventilation;

* use vacuum systems in machining operations;

* use pellets instead of powders wherever possible;

* use product substitution where possible;

* minimize the number of workers who have access to areas where there is a potential for beryllium exposure;

* monitor employee exposures to airborne beryllium dust and fume, using personal sampling techniques, on a regular basis to ensure that exposures are below the PELs and that proper respiratory protection is being used where necessary.

2. Work Practices to reduce beryllium exposure

Employers should ensure that employees use the following safe practices to reduce their exposure to beryllium:

* use high-efficiency particulate air (HEPA) vacuums to clean equipment and the floor around their work areas;

* do not leave a film of dust on the floor after the water dries if a wet mop is used to clean;

* do not use long vacuum hoses and do not loop the hoses that are used;

* do not disconnect or disable the vacuum system during any machining operation;

* never use compressed air to clean parts or working surfaces;

* avoid prolonged skin contact with beryllium particulate; and

* do not allow workers to eat, drink, smoke, or apply cosmetics at their work stations.

3. Hygiene and Personal Protective Clothing

OSHA is aware of CBD cases that have occurred among family members of beryllium-exposed workers. To reduce "carry-home" exposures, employers should provide showers, clean work clothes, and clean areas for storing street clothes. Protective clothing should be provided to employees who work in areas where beryllium-containing powders are used and where there is a potential for spills. In addition, employers should ensure that employees:

* change into work uniforms before entering their work area;

* place their uniforms in a labeled bin with a cover at the end of the work shift;

* shower and change into street clothes prior to leaving the facility;

* wash their face, hands, and forearms before eating, smoking, or applying cosmetics;

* keep their work clothes as clean as possible during the workshift;

* wipe off their shoes before leaving the work area; and

* do not wear their work uniform (including their work shoes) outside of the facility.

4. Respiratory Protection

Recent data suggest that exposures to beryllium even at levels below the 2 micrograms/m3 PEL may have caused CBD in some workers. Therefore, employers should consider providing their beryllium-exposed workers with air-purifying respirators equipped with 100-series filters (either N-, P-, or R-type) or, where appropriate, powered air-purifying respirators equipped with HEPA filters, particularly in areas where material containing beryllium can become airborne.

5. Training

Employers should give employees exposed to beryllium training and information about the following items:

* material safety data sheets (MSDSs) for beryllium;

* the fatal lung disease that may occur as a result of exposure;

* the availability of the BeLPT blood test to determine whether an exposed worker has become sensitized to beryllium;