The Heart of the Jungle is an ancient gemstone that was once owned by the Arumbayas, a pre-Colombian tribe in South America who believed it to have magical healing powers. It appears in the tv show episode The Broken Ear.
During his expedition, European explorer A.J. Walker was shown the gem after gaining the Arumbayas trust. Walker's guide, Lopez subsequently stole the stone and hid it inside the Idol of the Broken Ear. The Arumbayas gave chase to Walker's party after learning of its theft, resulting in Lopez's abandonment of the idol.
The idol was left in the posession of Walker, who brought it to Europe. For many decades the gem remained inside the idol at the Museum of Ethnography in Brussels until it was stolen by Rodrigo Tortilla (or Lopez in the TV episode), who came in pursuit of the gemstone. Tintin first learned of the gem when he met the Arumbayas and was told the story by Ridgewell. Upon returning to Europe he learned that the real fetish had until recently been in the posession of Simon Balthazar.
Balthazar had only just recently sold the true idol to Samuel Goldbarr. In pusuit of the gem Ramon Bada, Alonso Perez and Tintin followed Goldbarr onto the ship he was travelling on, the S.S. Washington. Following a confrontation between the two parties the idol broke and the gem fell overboard and sank to the bottom of the Atlantic Ocean.