Praise be to Allah.
The primary purpose of the Qur’aan is to guide mankind to Allaah, so that they will affirm His Oneness and worship Him alone, and attain His Paradise and His pleasure. The Qur’aan is not a book of science, medicine or astronomy, even though its verses may contain a little of such things.
Hence the Muslim should not let himself be distracted from the greater purpose of reciting the Qur’aan and look for the number of stones or rivers or kinds of animals mentioned therein.
Some precious stones such as rubies, pearls and coral are mentioned in the Qur’aan.
Allaah says (interpretation of the meaning):
“(In beauty) they are like rubies and coral”
“Out of them both come out pearl and coral”
“Like unto preserved pearls”
“And round about them will (serve) boys of everlasting youth. If you see them, you would think them scattered pearls”
These stones do not have any spiritual significance, rather they are mentioned in the Qur’aan to explain the blessings that Allaah has bestowed upon His slaves, of the seas and the things that are brought forth from them, or as a metaphor – so al-hoor al-‘iyn are likened to rubies, coral and preserved pearls, combining the purity of rubies and the whiteness of pearls and coral.
The boys are likened to scattered pearls, to indicate their beauty and good looks.
And Allaah knows best.