include the minerals common to known asteroids and
meteorites, plus many
minerals only (or at least primarily) found in meteorites. Note that many -
likely most - minerals on Earth are the result of many cycles of formation,
breakdown, and reformation under changing conditions including the presence of
liquid water and free oxygen, and thus could not exist in primitive materials.
As few as 60 distinct minerals may have initially formed in the early solar
system, with the remaining thousands of known minerals all formed by subsequent
reprocessing - many of which may only be possible as a result of the changes
created by life on Earth, including the presence of free oxygen.
(See The Evolution of Minerals.)
Chondrites (primitive asteroids including most stony meteorites) come in several varieties.
largely mimic the elemental composition of the solar nebula, minus the lighter volatiles.
Their spectra often reveal evidence of the (past) presence of liquid water in
the form of iron-rich clays,
serpentine group minerals such as cronstedtite (Fe2+2Fe3+(Si,Fe3+O5)(OH)4),
and the carbonate minerals
and siderite (FeCO3).
The ordinary chondrites largely mimic the composition of the Earth's mantle, and
generally include a mixture of chondrules that
each formed under either reducing and
oxidizing conditions. Minerals include
metallic iron (Fe), and
troilite (FeS) when formed under reducing conditions,
and olivine ((Mg,Fe)2SiO4),
and magnetite (Fe3O4)
when formed under oxidizing conditions.
Enstatite group carbonaceous chondrites contain some of the most reduced
minerals known, including osbornite (TiN),
schreibersite ((Fe, Ni)3P),
niningerite (MgS), and
perryite (Fe-Ni silicide).
The light-colored Calcium-Aluminum-rich Inclusions (or CAI's)
common in carbonaceous chondrites are composed of refractory minerals including
pyroxenes such as
hedenbergite (CaFeSi2O6) and
and additional forsterite-rich
olivine (very little iron is present).
Iron and stony-iron meteorites differ largely by the presence of stony material such as
including the gem variety peridot
in pallasite meteorites. The iron is always alloyed with nickel in proportions
ranging from 5% to as much as 25%. As they slowly cooled, the different alloys
might separate (thus
visible in Widmanstatten patterns) into the minerals
kamacite (Fe0.9Ni0.1) and
Even iron meteors commonly contain inclusions such as
and cohenite ((Fe,Ni,Co)3C).
There are many minerals commonly found in meteorites (and thus asteroids) which are
extremely rare on Earth, including
schreibersite (Fe,Ni)3P, and
Tiny diamonds (C)
have also been found in meteorites, but the most common gemstone found in
meteors by far is peridot
(the gem variety of olivine); some stony-iron meteors may be sliced and polished resulting in a
beautiful stained-glass-window appearance of green peridot crystals in an iron