Scrutinyite is a rare oxide mineral and is the alpha crystalline form of

lead dioxide Lead(IV) oxide is the inorganic compound with the formula PbO2. It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms. It has several important applicatio ...

(α-PbO₂),

plattnerite Plattnerite is an oxide mineral and is the beta crystalline form of lead dioxide (β-PbO2), scrutinyite being the other, alpha form. It was first reported in 1845 and named after German mineralogist Karl Friedrich Plattner. Plattnerite forms bun ...

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

(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 ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ke ...

and Mapimí, Durango,

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. 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 A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

consisted of crystalline plates 25–30

micrometers The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

(µm) across and 1–2 µm thick with the total weight below 1 mg. The flakes were collected from a

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

, limonite and

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 wa ...

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).

Characterization

The PbO₂ composition of scrutinyite was deduced by

energy-dispersive X-ray spectroscopy Energy-dispersive X-ray spectroscopy (EDS, EDX, EDXS or XEDS), sometimes called energy dispersive X-ray analysis (EDXA or EDAX) or energy dispersive X-ray microanalysis (EDXMA), is an analytical technique used for the elemental analysis or chemi ...

. 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 In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

groups. The crystal structure was deduced by XRD as orthorhombic,

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

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.

References

{{Reflist, 2

External links

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