F-type asteroids have spectra generally similar to those of the
B-type asteroids, but lack the "water" absorption feature around 3 μm indicative of hydrated minerals, and differ in the low wavelength part of the
ultraviolet spectrum below 0.4 μm. The
F-type and
B-type asteroids are not distinguishable with the criteria used in the
SMASS classification, so in that scheme are grouped together under the
B-type. ==See also==