Sentence:  Brazil's <WSD>carbonadoes</WSD> are indispensable today for the speedy cutting of hard rubber, bakelite and fiber compounds. Their absolute precision is especially valuable in turning such instruments as high-power telescopes and microscope tubes. 
Meaning of the word marked with <WSD> tags:  A dark, non-transparent, impure form of polycrystalline diamond (also containing graphite and amorphous carbon) used in drilling.