thumb|[[433 Eros, an example of an S-type asteroid]]
S-type (stony-type or siliceous-type) asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the second-most common after the carbonaceous C-type.
Characteristics
S-type asteroids, with an astronomical albedo of typically 0.20,
S-group asteroids
SMASS classification
In the SMASS classification, several generally "stony" types of asteroids are brought together into a wider S-group which contains the following types:
- A-type
- K-type
- L-type
- Q-type
- R-type
- a "core" S-type for asteroids having the most typical spectra for the S-group
- Sa, Sk, Sl, Sq, and Sr-types containing transition objects between the core S-type and the A, K, L, Q, and R-types, respectively. The entire "S"-assemblage of asteroids is spectrally quite distinct from the carbonaceous C-group and the often metallic X-group.
Tholen classification
In the Tholen classification, the S-type is a very broad grouping which includes all the types in the SMASS S-group except for the A, Q, and R, which have particularly strong "stony" absorption features around 1 μm.
Stony asteroid families
Prominent stony asteroid families with their typical albedo are the:
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