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Formula: Sc4Zr3O12
Oxide of scandium and zirconium,
well-known as a synthetic compound.
Crystal System: Trigonal
Specific gravity: 4.84 calculated
Environments
Allendeite was approved in 2007.
Localities
The Ningqiang meteorite, Ningqiang County, Hanzhong, Shaanxi, China, is a
carbonaceous chondrite. This is the first report of
hibonite-rich inclusions in Ningqiang. They exhibit three textural forms:
aggregates of euhedral hibonite single crystals,
fine-grained aggregates of subhedral hibonite with minor
spinel, and
hibonite aluminium-,
titanium-diopside
spinel spherules.
Opaque assemblages, formed by secondary alteration of
pre-existing alloys on the parent body, are widespread in chondrules (spheroidal mineral grains present in
large numbers in some stony meteorites) and matrix. On the other hand,
nepheline and sodalite, existing in
all chondritic components, formed by alkali-halogen metasomatism in the solar nebula
(Meteoritics & Planetary Science, 44.5.763-780).
At the type locality, the Allende meteorite, Pueblito de Allende, Chihuahua, Mexico, two new minerals,
allendeite and hexamolybdenum, were discovered, both occuring
as micro- to nano- crystals in an ultra-refractory inclusion.
The two minerals reflect conditions during early stages of the formation of the Solar System. Allendeite may
have been an important ultra-refractory carrier phase linking zirconium-,
scandium- oxides to the more common
scandium-, zirconium- enriched
pyroxenes in calcium-aluminium-rich
inclusions
(AM 99.4.654-666).
Associated minerals include perovskite,
osmium - iridium -
molybdenum - tungsten alloys and
scandium-stabilised tazheranite
(HOM).
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