Pitchblende schlema-alberoda.JPG
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Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a
chemical composition A chemical composition specifies the identity, arrangement, and ratio of the elements making up a compound. Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for ...
that is largely UO2 but because of oxidation typically contains variable proportions of U3O8.
Radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
of the uranium causes the mineral to contain
oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
s of lead and trace amounts of helium. It may also contain thorium and rare-earth elements.


Overview

Uraninite used to be known as pitchblende (from '' pitch'', because of its black color, and ''blende'', from ''blenden'' meaning "to deceive", a term used by German miners to denote minerals whose density suggested metal content, but whose exploitation, at the time they were named, was either unknown or not economically feasible). The mineral has been known at least since the 15th century from silver mines in the Ore Mountains, on the German/Czech border. The type locality is the historic mining and spa town known as Joachimsthal, the modern day Jáchymov, on the Czech side of the mountains, where F. E. Brückmann described the mineral in 1772. Pitchblende from the Johanngeorgenstadt deposit in Germany was used by M. Klaproth in 1789 to discover the element uranium. All uraninite minerals contain a small amount of radium as a
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
product of uranium. Marie Curie used pitchblende, processing tons of it herself, as the source material for her isolation of radium in 1910. Uraninite also always contains small amounts of the lead isotopes 206Pb and 207Pb, the end products of the decay series of the uranium isotopes 238U and 235U respectively. Small amounts of helium are also present in uraninite as a result of alpha decay. Helium was first found on Earth in
cleveite Cleveite is an impure radioactive variety of uraninite containing uranium, found in Norway. It has the composition UO2 with about 10% of the uranium substituted by rare-earth elements. It was named after Swedish chemist Per Teodor Cleve. Cleveit ...
, an impure radioactive variety of uraninite, after having been discovered spectroscopically in the
Sun's atmosphere The Sun is the star at the center of the Solar System. It is a nearly perfect ball (mathematics), ball of hot plasma (physics), plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as ...
. The extremely rare elements technetium and
promethium Promethium is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth's crust at any given time. Promethium is one of onl ...
can be found in uraninite in very small quantities (about 200  pg/kg and 4  fg/kg respectively), produced by the
spontaneous fission Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...
of
uranium-238 Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it ...
. Francium can also be found in uraninite at 1
francium Francium is a chemical element with the symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223 (originally called actinium K after the natural decay chain it appears in), has a half-life of only 22&nb ...
atom for every 1 × 1018 uranium atoms in the ore as a result from the decay of actinium.


Occurrence

Uraninite is a major ore of uranium. Some of the highest-grade uranium ores in the world were found in the Shinkolobwe mine in the Democratic Republic of the Congo (the initial source for the Manhattan Project) and in the Athabasca Basin in northern Saskatchewan, Canada. Another important source of pitchblende is at Great Bear Lake in the
Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...
of Canada, where it is found in large quantities associated with silver. It also occurs in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, the Czech Republic, Germany, England,
Rwanda Rwanda (; rw, u Rwanda ), officially the Republic of Rwanda, is a landlocked country in the Great Rift Valley of Central Africa, where the African Great Lakes region and Southeast Africa converge. Located a few degrees south of the Equator ...
, Namibia and South Africa. In the United States, it can be found in the states of Arizona, Colorado, Connecticut, Maine, New Hampshire, New Mexico, North Carolina and Wyoming. The geologist
Charles Steen Charles Augustus Steen (December 1, 1919 – January 1, 2006) was a geologist who made and lost a fortune after discovering a rich uranium deposit in Utah during the uranium boom of the early 1950s. Early years Charlie Steen was born in 1919 ...
made a fortune on the production of uraninite in his Mi Vida mine in Moab, Utah. Uranium ores from the Ore Mountains (today the border between the Czech Republic and Germany) were an important supply of both the wartime
German nuclear program The Uranverein ( en, "Uranium Club") or Uranprojekt ( en, "Uranium Project") was the name given to the project in Germany to research nuclear technology, including nuclear weapons and nuclear reactors, during World War II. It went through seve ...
(which failed to produce a bomb) and the Soviet nuclear program. Mining for uranium in the Ore Mountains (under the auspices of SDAG Wismut after the war) ceased after the collapse of the German Democratic Republic. Uranium ore is generally processed close to the mine into yellowcake, which is an intermediate step in the processing of uranium.


See also

* List of minerals * List of uranium mines * Thorianite * Uranium ore deposits


References


External links

* {{Ores Cubic minerals Minerals in space group 225 Oxide minerals Radioactive minerals Uranium(IV) minerals