6178 (1986 DA)

Reference:

Asteroid 1986 DA: Radar Evidence for a Metallic Composition.
Ostro, S. J., D. B. Campbell, J. F. Chandler, A. A. Hine, R. S. Hudson, K. D. Rosema, and I. I. Shapiro.
Science 252, 1399-1404 (1991).

Abstract

Echoes from the near-earth object 1986 DA show it to be significantly more reflective than other radar-detected asteroids. This result supports the hypothesis that 1986 DA is a piece of NiFe metal derived from the interior of a much larger object that melted, differentiated, cooled, and subsequently was disrupted in a catastrophic collision. This 2-kilometer asteroid, which appears smooth at centimeter to meter scales but extremely irregular at 10- to 100-meter scales, might be (or have been a part of) the parent body of some iron meteorites.


See also this ranking of near-earth-asteroid radar albedos.