Scrutinyite is a rare

oxide mineral The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. The minerals with complex anion groups such as the si ...

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.

Identification

The synthetic

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

form of lead dioxide, α-PbO₂, was known from 1941. Although natural lead dioxide has been known, as the mineral plattnerite (β-PbO₂), since 1845,Haidinger W (1845
Zweite Klasse: Geogenide. II. Ordnung. Baryte VII. Bleibaryt. Plattnerit.
p. 500 in Handbuch der Bestimmenden Mineralogie Bei Braumüller and Seidel Wien pp. 499-506 (in German) 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 Mapimí () is a city and municipal seat of the Mapimí Municipality in the Mexican state of Durango. As of 2015, the town of Mapimí had a population of 5,623. The Ojuela Mine, about southeast of Mapimí, is a famous locality for mineral speci ...

, Mexico. It was first thought to be minium (

lead tetroxide Lead(II,IV) oxide, also called red lead or minium, is the inorganic compound with the formula Pb3O4. A bright red or orange solid, it is used as pigment, in the manufacture of batteries, and rustproof primer paints. It is an example of a mixed ...

mineral) because of its high lead content, brown color and association with other lead oxide minerals plattnerite and

murdochite Murdochite is a mineral combining lead and copper oxides with the chemical formula (x ≤ 0.5). It was first discovered in 1953 in the Mammoth-Saint Anthony Mine in Pinal County, Arizona by Percy W. Porter, a mining engineer who h ...

. Its holotype specimen consisted of crystalline plates 25–30 micrometers (µm) across and 1–2 µm thick with the total weight below 1 mg. The flakes were collected from a fluorite, quartz,

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

and rosasite matrixes. Identification and characterization of scrutinyite by the standard

X-ray diffraction X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

(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 spectroscopy. 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 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 ...

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.

References

{{Reflist, 2

External links

Spectroscopic data on Scrutinyite
Oxide minerals Orthorhombic minerals Minerals in space group 60