Final answer:
The 'mine of jewels' or Ratnakara in Sanskrit texts refers to the Indian Ocean, which was central to maritime trade and the Red Sea was pivotal for trade between Himyar and Aksum.
Step-by-step explanation:
In Sanskrit texts, the ocean referred to as Ratnakara, meaning the 'mine of jewels,' is the Indian Ocean. This ocean has historically been a center for maritime trade and cultural exchange, connecting regions like India to East Africa, the Middle East, and Southeast Asia. Furthermore, regarding the body of water that allowed Himyar and Aksum to conduct long-distance sea trade, the correct answer would be the Red Sea. This sea was a critical maritime route for trade and exchange between these civilizations and others located around the Indian Ocean basin.