Encyclopedia of the Solar System 2nd ed

Meteorites 253

(a) (b)

FIGURE 1 Fusion crusts: (a) Noblesville H chondrite; (b) Lafayette Martian meteorite.
Noblesville, which fell on 31 August 1991, has nearly complete fusion crust but exposed surface at
lower right next to the 1-cm cube shows a genomict (H6 in H4) breccia. (Photo courtesy of NASA
Johnson Space Center.) Lafayette exhibits very delicate, redeposited droplets on its sides,
indicating an orientation with its top pointing Earthward late in atmospheric traversal. (Photo
courtesy of the Smithsonian Institution.)

University by O. C. Farrington (a prominent meteoriticist),
the chemistry professor on whose desk it was found thought
it a terrestrial glacial artifact. Who actually recovered this
martian meteorite is a mystery.
Meteorites derive from asteroids and, less commonly,
from larger parent bodies: 18 individual samples represent-

ing 31 separate falls (all but 5 from Antarctica) come from

Earth’s Moon; and 32 others (6 from Antarctica) almost cer-

tainly are from Mars [seeMars:Surface andInterior;

TheMoon]. Some interplanetary dust particles may also

come from these sources, and/or comets. Meteorites are

rocks and therefore polymineralic (Table 2), with each of

TABLE 2 Common Meteoritic or Cited Minerals

Mineral Formula Mineral Formula Mineral Formula

Anorthite CaAl 2 Si 2 O 8 Hibonite CaAl 12 O 19 Pyroxene solid solution

Clinopyroxene (Ca,Mg,Fe)SiO 3 Ilmenite FeTiO 3 enstatite (En) MgSiO 3

Chromite FeCr 2 O 4 Kamacite α-(Fe,Ni) ferrosilite (Fs) FeSiO 3

Cohenite (Fe,Ni) 3 C Lonsdaleite C wollastonite (Wo) CaSiO 3

Cristobalite SiO 2 Magnetite Fe 3 O 4 Schreibersite (Fe,Ni) 3 P

Diamond C Melilite solid solution Serpentine (chlorite) (Mg,Fe) 6 Si 4 O 10 (OH) 8

Diopside CaMgSi 2 O 6 ̊akermanite (Ak) ̊ Ca 2 MgSi 2 O 7 Spinel MgAl 2 O 4

Enstatite MgSiO 3 gehlenite (Ge) Ca 2 Al 2 SiO 7 Spinel solid solution

Epsomite MgSO 4 ·7H 2 O Oldhamite CaS spinel MgAl 2 O 4

Fayalite Fa 2 SiO 4 Olivine (Mg,Fe) 2 SiO 4 hercynite FeAl 2 O 4

Feldspar solid solution Olivine solid solution chromite FeCr 2 O 4

albite (Ab) NaAlSi 3 O 8 fayalite (Fa) Fe 2 SiO 4 Taenite γ-(Fe,Ni)

anorthite (An) CaAl 2 Si 2 O 8 forsterite (Fo) Mg 2 SiO 4 Tridymite SiO 2

orthoclase (Or) KAlSi 3 O 8 Orthopyroxene (Mg,Fe)SiO 3 Troilite FeS

Ferrosilite FeSiO 3 Pentlandite (Fe,Ni) 9 S 8 Whitlockite Ca 3 (PO 4 ) 2

Forsterite Mg 2 SiO 4 Plagioclase

Gehlenite Ca 2 Al 2 SiO 7 albite (Ab) NaAl 2 Si 2 O 8

Graphite C anorthite (An) CaAl 2 Si 2 O 8