In chapter IV of John Steinbeck's The Pearl we witness Kino and Juana getting ready to sell the pearl. In typical small-town tradition, everybody has already gotten the news about Kino's finding as well as about his wish to sell the huge pearl.
In this chapter we can almost perceive the danger lurking beneath the surface: People are too aware of Kino and Juana's plans and, as a result, they miss work, and follow them. The entire town of La Paz is in on it. Everything has stopped for the sake of Kino, Juana, and the pearl.
When Kino and Juana, as well as Kino's brother, go to the village to sell the pearl they are consistently told that the pearl is worthless because it is too big. Both brothers remember that people have tried to scam the pearl sellers before, and this adds to the danger of Kino's situation.
Finally, the most important part of the chapter occurs when Kino is actually assaulted for the pearl by a complete stranger. If the whole town knows already that the pearl was deemed unworthy, why would Kino have hidden enemies looking for it? Either way, this is significant in that Juana begins to change her mind about the pearl and beseeches Kino to throw it back in the water. Kino, despite of the beating he gets, says for the first time "I am a man" consistently, which basically means that he is willing to risk his life for the pearl. In all, the importance of the chapter is that it shows that the pearl is not a blessed finding as we think at first. It can actually put you in a grave danger.