D-type asteroids have a very low albedo and a featureless reddish electromagnetic spectrum. It has been suggested that they have a composition of organic rich silicates, carbon and anhydrous silicates, possibly with water ice in their interiors. D-type asteroids are found in the outer asteroid belt and beyond; examples are 152 Atala, 588 Achilles, 624 Hektor and 944 Hidalgo.

In 1992, Larry A. Lebofsky and colleagues published an article in which they detected a spectral feature at 3 micrometres in 773 Irmintraud, a main-belt D-type asteroid. This feature was believed to indicate the presence of water on the surface and to indicate that the D-type asteroid was more likely to be in an altered state rather than in an unaltered, primitive or primordial state.

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