The Jewish Mob is a criminal organization which deals in diamond trading. Isaac Roth, a Hasidic Jew, appears to be the boss of the operation, with Mori Green, a mainstream Orthodox Jew, as the underboss and his right hand man. All members of the Jewish Mob have suits with ties, with non-matching jeans. They can appear in two forms: A bald fat man, or one smaller, with short hair. Their vehicle of choice are black PMP 600's. The LCPD database says that Roth, Green and the Jewish Mob in general make frequent deals with African warlord Claude Wome, a dealer in conflict diamonds.
Events of GTA IV
The diamond deal
In their first mission appearance, which coincidentally is the Impossible Trinity trio of missions (Museum Piece in GTA IV, Collector's Item in TLAD & Not so Fast in TBOGT), they are dealing 2 Million Dollars for Ray Boccino's Diamonds. Ray sends Niko Bellic & Johnny Klebitz to do the deal; when Luis Lopez shoots up the deal killing Mori Green, the museum turns into a firefight as Luis steals the diamonds, Johnny steals the money and Niko flees with nothing.
Later, Issac Roth blames Ray Boccino for botching the deal and taking the money and diamonds for himself (when in reality this was Johnny's fault). After an argument, Roth threatens Boccino. In response to this, Boccino, in the mission Late Checkout, sends Niko Bellic to kill Roth and his Diamond Dealers at the Majestic Hotel.