SOLVED. Adventure book read in the 1980s, possibly set in early 20th century. Quest group go into jungle, they find a tribe who worships a crocodile and they have precious gems. Tribe throws in adventurers to crocodile. Think they all survive and escape.

[Asma]

Members of the quest group are an adventurer male, a female (i think they find in the jungle) and a tribal slave?
Cant remember if the gems found with the crocodile are rubies or sapphires.
The tribal slave makes a knife which they use to kill the crocodile when they are thrown in to the cave?
Thanks for helping!

[Asma]

I found it! H Rider Haggard authored People Of The Mist.
Excited to read it again :-)

[Rainbowheart]

Glad you found it!

The People of the Mist for the link.