Andersonite
Encyclopedia
Andersonite, Andersonit or Andersonita (Na2CaUO2(CO3)3•6H2O), or hydrated sodium
calcium
uranyl
carbonate
is a rare uranium carbonate
mineral that was only described in the last half century. Named for Charles Alfred Anderson (1902-1990) of United States Geological Survey
, who first described the mineral species, it is found in sandstone
-hosted uranium deposits. It has a high vitreous to pearly luster
and is very fluorescent. Andersonite specimens will usually glow a bright lemon yellow (or green with blue hints depending on the deposit) in ultraviolet
light. The mineral is formed as a secondary mineral and as an efflorescent crust in uranium mines. It is commonly found as translucent small rhombohedral crystals that have angles close to 90 degrees although its crystal
system is nominally trigonal. Its Mohs hardness
is 2.5, with an average Specific Gravity
of 2.9.
Andersonite is formed as an efflorescent crust in the dry air of uranium mines. Thus, andersonite specimens are a secondary mineral being the result of human intervention, and these specimens are not considered by some mineral collectors to be a true natural mineral
. As this mineral is water-soluble, samples must be stored in dry conditions.
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
uranyl
Uranyl
The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula [UO2]2+. It has a linear structure with short U-O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands are bound to the uranyl ion in an equatorial plane...
carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
is a rare uranium carbonate
Uranium carbonate
Uranyl carbonate, UO2, is a carbonate of uranium that forms the backbone of several uranyl mineral species such as Andersonite, McKelveyite and Wyartite and most importantly Rutherfordine...
mineral that was only described in the last half century. Named for Charles Alfred Anderson (1902-1990) of United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
, who first described the mineral species, it is found in sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
-hosted uranium deposits. It has a high vitreous to pearly luster
Lustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
and is very fluorescent. Andersonite specimens will usually glow a bright lemon yellow (or green with blue hints depending on the deposit) in ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light. The mineral is formed as a secondary mineral and as an efflorescent crust in uranium mines. It is commonly found as translucent small rhombohedral crystals that have angles close to 90 degrees although its crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
system is nominally trigonal. Its Mohs hardness
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
is 2.5, with an average Specific Gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of 2.9.
Andersonite is formed as an efflorescent crust in the dry air of uranium mines. Thus, andersonite specimens are a secondary mineral being the result of human intervention, and these specimens are not considered by some mineral collectors to be a true natural mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
. As this mineral is water-soluble, samples must be stored in dry conditions.