Scrutinyite
Encyclopedia
Scrutinyite is a rare oxide mineral
and is the alpha crystalline form of lead dioxide (α-PbO2), plattnerite
being the other, beta form. The mineral was first reported in 1988 and its name reflects the scrutiny and efforts required to identify it from a very limited amount of available sample material.
(β-PbO2), since 1845, its alpha form could only be recognized in 1981 and reliably identified in 1988.
The new mineral was spotted in several samples collected at Bingham, New Mexico
and Mapimí, Durango, Mexico
. It was first thought to be minium
(lead tetroxide mineral) because of its high lead content, brown color and association with other lead oxide minerals plattnerite and murdochite
. Its holotype specimen consisted of crystalline plates 25–30 micrometers across and 1–2 microns thick with the total weight below 1 mg. The flakes were collected from a fluorite
, quartz
, limonite
and rosasite
matrixes. Identification and characterization of scrutinyite by the standard X-ray diffraction
(XRD) technique was hindered by scarcity of material and strong signal interference with plattnerite. The unusual amount of effort required for the analysis resulted in its name derived from the word "scrutiny". The holotype specimen is preserved in the US National Museum (catalog number NMNH 165479).
. Slight oxygen deficiency is generally attributed to the surface effects, especially in thin samples, namely oxygen in the surface layers of PbO2 is usually substituted by the hydroxyl
groups.
The crystal structure was deduced by XRD as orthorhombic, space group
Pbcn (No. 60), Pearson symbol
oP12, lattice constants a = 0.497 nm, b = 0.596 nm, c = 0.544 nm, Z = 4 (four formula units per unit cell) were in reasonable agreement with previous results obtained on synthetic samples.
Oxide mineral
The oxide mineral class includes those minerals in which the oxide anion is bonded to one or more metal ions. The hydroxide bearing minerals are typically included in the oxide class...
and is the alpha crystalline form of lead dioxide (α-PbO2), plattnerite
Plattnerite
Plattnerite is an oxide mineral and is the beta crystalline form of lead dioxide , scrutinyite being the other, alpha form. It was first reported in 1845 and named after German mineralogist Karl Friedrich Plattner...
being the other, beta form. The mineral was first reported in 1988 and its name reflects the scrutiny and efforts required to identify it from a very limited amount of available sample material.
Identification
The synthetic orthorhombic form of lead dioxide, α-PbO2, was known from 1941. Although natural lead dioxide has been known, as the mineral plattneritePlattnerite
Plattnerite is an oxide mineral and is the beta crystalline form of lead dioxide , scrutinyite being the other, alpha form. It was first reported in 1845 and named after German mineralogist Karl Friedrich Plattner...
(β-PbO2), since 1845, its alpha form could only be recognized in 1981 and reliably identified in 1988.
The new mineral was spotted in several samples collected at Bingham, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
and Mapimí, Durango, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It was first thought to be minium
Minium (mineral)
Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4. It is a light to vivid red and may have brown to yellow tints. It typically occurs as scaly to earthy masses. It crystallizes in the tetragonal crystal system....
(lead tetroxide mineral) because of its high lead content, brown color and association with other lead oxide minerals plattnerite and murdochite
Murdochite
Murdochite is a mineral combining lead and copper oxides with formula PbCu6O8-x2x.It was first discovered in 1953 in the Mammoth-Saint Anthony Mine in Pinal County, Arizona. It was named for Joseph Murdoch , American mineralogist....
. Its holotype specimen consisted of crystalline plates 25–30 micrometers across and 1–2 microns thick with the total weight below 1 mg. The flakes were collected from a fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, limonite
Limonite
Limonite is an ore consisting in a mixture of hydrated iron oxide-hydroxide of varying composition. The generic formula is frequently written as FeO·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide.Together with hematite, it has...
and rosasite
Rosasite
Rosasite is a carbonate mineral with minor potential for use as a zinc and copper ore. Chemically, it is a copper zinc carbonate hydroxide with a copper to zinc ratio of 3:2, occurring in the secondary oxidation zone of copper-zinc deposits. It was originally discovered in 1908 in the Rosas mine in...
matrixes. Identification and characterization of scrutinyite by the standard X-ray diffraction
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
(XRD) technique was hindered by scarcity of material and strong signal interference with plattnerite. The unusual amount of effort required for the analysis resulted in its name derived from the word "scrutiny". The holotype specimen is preserved in the US National Museum (catalog number NMNH 165479).
Characterization
The PbO2 composition of scrutinyite was deduced by energy-dispersive X-ray spectroscopyEnergy-dispersive X-ray spectroscopy
Energy-dispersive X-ray spectroscopy is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on the investigation of an interaction of a some source of X-ray excitation and a sample...
. Slight oxygen deficiency is generally attributed to the surface effects, especially in thin samples, namely oxygen in the surface layers of PbO2 is usually substituted by the hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups.
The crystal structure was deduced by XRD as orthorhombic, space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
Pbcn (No. 60), Pearson symbol
Pearson symbol
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W.B. Pearson. The symbol is made up of two letters followed by a number. For example:* Diamond structure, cF8...
oP12, lattice constants a = 0.497 nm, b = 0.596 nm, c = 0.544 nm, Z = 4 (four formula units per unit cell) were in reasonable agreement with previous results obtained on synthetic samples.