Carbonado: natural polycrystalline diamond

Science. 1969 Aug 22;165(3895):799-802. doi: 10.1126/science.165.3895.799.

Abstract

Carbonados are porous aggregates of mostly xenomorphic diamond crystallites ranging in diameter from a fraction of a micron to over 20 microns. Crystalline inclusions (up to 3 percent) occur in the pores of the crystallites and consist mainly of orthoclase and small amounts of other igneous, metamorphic, and secondary minerals.