203. The "Black" Radical: 黒

We can read this radical as くろ or, when it's on the left side of a kanji, くろへん.

Of all the Joyo kanji, the "black" radical 黒 is on duty only in 黙 (1856: silent). In fact, according to some sources, 黒 acts as both the radical and the phonetic in 黙! 

In 墨 (1821: black inkstick; black ink; Mexico), the 黒 is a mere component.

By the way, essay 1227 on 玄 (mysterious) explains that whereas 玄 (radical 95) is the “blackness” radical, 黒 is the “black” radical.